(Coleóptera: Chrysomelidae) and Their Amaranthaceous Hosts

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/^^x UNITED STATES TECHNICAL PREPARED BY (iLyi) DEPARTMENT OF BULLETIN SCIENCE AND ^^»^ AGRICULTURE NUMBER 1593 EDUCATION ADMINISTRATION

Probable Evolution and Morphological Variation in South American Disonychine Flea Beetles (Coleóptera : Chrysomelidae) and Their Amaranthaceous Hosts ^

Document Delivery Services Branch USDA, National Agricultural Library Nal B!dg. 10301 Baltimore Blvd. Beltsville. MD 20705-2351 Floating-mat gi-owth habit of alligatorweed. A, Alligatorweed growing in pure stand as floating mats prior to establishment of biocontrol agents at Blue Lake, an oxbow lake, in the Yazco Basin of the Mississippi River alluvial plain near Itta Bena, Miss. B, The reach of alligatorweed from the floating-mat edge is comparable to the free-ñoating Altenia»tl>em hasslerifnia. the closest relative of alligatorweed. From the mat margin, erect stems increase in length toward the maximum attained in the mat interior. Compare the length of ascending stems with that shown in figure 7. Probable Evolution and Morphological Variation in South American Disonychine Flea Beetles (Coleóptera : Chrysomelidae) and Their Amaranthaceous Hosts

G. B. Vogt, research entomologist, J. U. McGuire, Jr., mathematical statistician, and A. D. Cushman, scientific illustrator

Science and Education Administration

USD A Technical Bulletin No. 1593

UNITED STATES DEPARTMENT OF AGRICULTURE Science and Education Administration in cooperation with Mississippi Agricultural and Forestry Experiment Station Trade names are used in this publication solely for the purpose of providing specific information. Mention of a trade name does not constitute a guarantee or warranty of the product by the U.S. Department of Agriculture or an endorse- ment by the Department over other products not mentioned.

Washington, D.C. Issued June 1979 For sale by the Superintendent of Documents, U.S. Government Printing Office, Washington, D.C. 20402 CONTENTS

Page Abstract xi Acknowledgments xiii

INTRODUCTION 1

RELATIONSHIPS AMONG FLEA BEETLES AND THEIR HOST PLANTS 3 Some Host-Plant Characteristics 3 Pupation of Agasicles Species in Host-Plant Stems 4 Affinities Between Agasicles and Disonycha 11 Biogeography of Flea Beetles and Their Host Plants 13 Ecological and Evolutionary Considerations Within A^asic/^s 27

PROPOSED EVOLUTIONARY DENDROGRAMS FOR FLEA BEETLES AND THEIR HOST PLANTS 32 Suggested Coevolutionary Course 32 Alternatives to Coevolution 36

MORPHOLOGICAL VARIATION IN FLEA BEETLES AND THEIR HOST PLANTS 41 Measurement of Plants 41 Measurement of Flea Beetles 41 Correlation of Characters 44 Plants 44 Flea beetles (recognized species) 49 Flea beetles (subspecific forms of Agasicles opaca) 76 Proposed trifúrcate representation for the phenoclines 103

SUMMARY AND CONCLUSIONS 118

Literature Cited 133 Appendix 136 Analytical data for measured flea beetle and amphibious amaranth characters 136 Specific names referred to in text, with authors 148 ILLUSTRATIONS

Fig. Page Floating-mat growth habit of alHgatorweed Frontispiece 1-6. Important specialized South American flea beetles of amphibious amaranths 5 7. Procumbent floating growth habit of the amphibious amaranth Altemanthera hassleriana 6 8-15. Two more flea beetles of amphibious amaranths, a coccinellid predator, and disonychine egg masses 7 16-25. Immature stages of disonychine flea beetles and related Chrys- omelidae 8 26-31. Aedeagi of specialized South American flea beetles of amphibious amaranths 9 32. South American distribution of alHgatorweed and Altemanthera hassleriana 14 33. Western Hemisphere distribution of the amphibious amaranths Altemanthera sessüis and A. obovata and of the combined halophytic amaranths Phüoxerus vermicularis and P. portulacoides 15 34. South American distribution of Agasicles species 16 35. Distribution of Disonycha argentinensis and Phenrica species, known herbivores of amphibious amaranths growing on terrestrial sites 17 36. Distribution of four closely related indigenous North American and South American species of Disonycha 19 37. Distribution of North American Disonycha xanthomelas 20 38. North American and South American distribution of Disonycha glabrata and closely related D. prolixa 21 39. Dendrogram of estimated evolutionary courses of four species of amphibious amaranths from a presumably terrestrial ancestral form 33 40. Alternative dendrograms of estimated evolutionary course of Di- sonycha argentinensis and five Agasicles species from an ancestral form resembling Z>. argentinensis 34 41-44. Variation in elytral markings of Agasicles hygrophila 35 45. Postulated evolutionary course of Disonycha glabrata and its ancestral forms and D. argentinensis and its ancestral forms 39 46. Characters measured in flea beetles 42 47. Stem size in South American amphibious amaranths, by length of ascending portion of stem and its basal diameter 45 48. Stem size in South American amphibious amaranths, by length and diameter at midpoint of stem internode reaching within 80 millimeters of terminal 46 49. Interactive evolution of amphibious amaranths and Agasicles species that pupate in the stem 48 ^^ë' Page Means and bivariate normal ellipses (first version) for relations in flea beetles between— 50. Pronotal width and length 52^3 51. Elytral length and width 54-55 52. Total body length and thickness 56-57 53. Head width and length 58^9 54. Interocular width and interantennal width 60-61 55. Maximum width of the base of the black U-shaped elytral marking and the minimum width of the base of the ivory U-shaped elytral marking 62-63 56. Antennal length and metathoracic tibial length 64-65 57. Lengths of fourth and third antennal segments 66-67 58. Lengths of sixth and fifth antennal segments 68-69 59. Length and width of seventh antennal segment 70-71 60. Pygidial width and length 72-73 61. Ten graded variants of elytral markings selected from the 137 specimens of Agasicles opaca studied quantitatively 79 Means and bivariate normal ellipses (second version) for relations in flea beetles between— 62. Pronotal width and length 82-^ 63. Elytral length and width 84 64. Total body length and thickness 85 65. Head width and length 86 66. Interocular width and interantennal width 88-^9 67. Maximum width of the base of the black U-shaped elytral marking and the minimum width of the base of the ivory U-shaped elytral marking 90-91 68. Antennal length and metathoracic tibial length 92 69. Lengths of fourth and third antennal segments 93 70. Lengths of sixth and fifth antennal segments 94-95 71. Length and width of seventh antennal segment 96-97 72. Pygidial width and length 98-99

73. Trifúrcate representation of relationship of existing Agasicles species 104 Trifúrcate (third-version) phenocline for the mean points of— 74. Pronotal width to pronotal length of flea beetles 106 75. Elytral length to elytral width of flea beetles 107 76. Total body length to body thickness of flea beetles 108 77. Head width to head length of flea beetles 108 78. Interocular width to interantennal width of flea beetles 109 79. Maximum width of the base of the black U-shaped elytral marking to the minimum width of the base of the ivory-colored U-shaped elytral marking of flea beetles 110 80. Antennal length to metathoracic tibial length of flea beetles Ill 81. Lengths of fourth to third antennal segments of flea beetles 112 82. Lengths of sixth to fifth antennal segments of flea beetles 113 Fig. Page 83. Length to width of seventh antennal segment of flea beetles 114 84. Pygidial width to pygidial length of flea beetles 115 85. Recent distribution of rain forests and open landscapes in the Neo- tropics 121 86. Distribution of presumed forest refugia in the Neotropics during dry climatic phases of the Pleistocene, based upon Recent occurrences of three diverse animal groups 122 87. Rain forest dispersal centers of terrestrial vertebrates in the Neo- tropics 123 88. Nonforested dispersal centers of terrestrial vertebrates in the Neo- tropics 124 TABLES

Page 1. Known host plants oí Altemanthera-oriented disonychine flea beetles (Disonychay Phenricüj and Agasicles) and D, conjuncta, one of many non-Alternanthera-oriented species 18 2. Characteristics of the genera that include the 11 recognized, most highly specialized species oriented to the amphibious amaranths in South America 24 3. Plant characters analyzed 41 4. Insect characters analyzed 43 5. First-version phenocline distances between mean points of character pairs of Agasicles species as shown in figures 50-60 76 6. Straight-line distances between mean points of body proportions of Disonycha argentinensis smd Agasicles species 77 7. Frequency distribution, in percentage of representation, of the 10 variants of elytral markings of Agasicles opaca illustrated in figure 61 80 8. Second-version phenocline distances between mean points of character pairs of Agasicles species as shown in figures 62-72 80 9. Total second-version phenocline distances for vittate species of Agasicles and for geographic forms of fasciate A. opaca as shown in figures 62-72 101. 10. Successive second-version phenocline distances between mean points of character pairs for vittate and fsisciate Agasicles species and Disonycha argentinensis as shown in figures 62-72 102 11. Female percentages of the combined female and male distances between each of the phenoclinal mean points given in table 10 for seven forms of Agasicles 103 12. Lengths of stem and 3 arms of the proposed trifúrcate phenocline as expressed by each of the 11 character pairs 105 13. Total third-version phenocline distances for vittate species of A^a- sicles and for geographic forms of fasciate A. opaca as shown in figures 74-^, illustrating the trifúrcate phenocline representation . 116 A-1. Composition of measured samples of host plants 136 A-2. Measurement reliability for four characters of Alternanthera philoxeroides and A. hassleriana herbarium specimens 138 A-3. Composition of measured samples of flea beetles 139 A^. Measurement reliability for 22 characters of preserved Agasicles hygrophila specimens .140 A-5. Means, standard deviations, and coefficients of correlation for the two pairs of characters measured in three Alternanthera species ... 141 A-6. Means, standard deviations, and coefficients of correlation for the 11 pairs of characters measured in females of the 6 flea beetle species 141 Page A-7. Means, standard deviations, and coefficients of correlation for the 11 pairs of characters measured in males of the 6 flea beetle species 143 A-8. Means, standard deviations, and coefficients of correlation for the measurements of pronotal width and length of the combined vittate Agasicles species 144 A-9. Composition of measured samples of Agasicles opaca supplemented in 1975 and divided into three geographic forms 145 A-10. Means, standard deviations, and coefficients of correlation for the 11 pairs of characters measured in females of 3 geographic forms of Agasicles opaca 146 A-11. Means, standard deviations, and coefficients of correlation for the 11 pairs of characters measured in males of 3 geographic forms of Agasicles opaca 147 ABSTRACT

PROBABLE EVOLUTION AND MORPHOLOGICAL VARIATION IN SOUTH AMERICAN DISONYCHINE FLEA BEETLES (COLE- ÓPTERA : CHRYSOMELIDAE) AND THEIR AMARANTHACEOUS HOSTS. G. B. Vogt, J. U. McGuire, Jr., and A. D. Cushman. U.S. Dep. Agrie. Tech. Bull. No. 1593, 148 pp. Address communications to G. B. Vogt, Southern Weed Science Laboratory, Science and Education Adm^inistration, Stoneville, Miss, 38776.

Agasicles has an obligatory feeding relationship with three amphibious amaranths, mohxámg Alternxinthera philoxeroides (Mart.) Griseb. There is no danger of host transfer in North America by Agasicles hygrophila Selman and Vogt. Disonycha argentinensis Jacoby is the closest extrageneric relative of Agasicles. These flea beetles diverged from a terrestrial ancestral form resembling D. argentinensis and coevolved with the amphibious amaranths. The plants were advanced in their evolution when Agasicles appeared. A trifúrcate distribution of forms resulted that centers on A. hygrophila. The middle arm consists of a polytypic fasciate species, Agasicles opaca Bechyné, which overlaps a vit täte species, A. hygrophila. The four vittate semispecies that comprise the side arms are geographically exclusive and constitute a superspecies. The vitiate Agasicles species have evolved primarily on alligatorweed centered in the lower basin of the Rio de la Plata. Having undergone most of its evolution interacting with small- stemmed alligatorweed, fasciate polytypic A. opaca diverged from the vittate forms, continuing its evolution interacting mostly with the oversized stems of Altemanthera hassleriana Chod., the closest relative of alligatorweed. While this release from interaction with small stems relates to an accelerated rate of divergence from the vittate forms, it also relates to slowed evolution of reproductive isolation and therefore speciation among the fasciate forms. Normal bivariate ellipses for 11 pairs of characters discriminate taxonomically between some of the vittate semispecies but not between forms of fasciate A. opaca. Apparently, interaction with the host-plant stem and the resulting rate of speciation drive the taxon cycle within Agasicles. Instrumental in speciation of the genus and concomitant in its evolution has been the seemingly de novo appearance and differentiation of the sexually dimorphic external genitalia. Speciation has not occurred in the other recognized specialized insect biotic agents of amphibious amaranths, which, like Agasicles y have geographic ranges that are nearly coextensive with that of alligatorweed in South America. These include Vogtia malloi Pastrana and Amynothrips andersoni O'Neill, both of monotypic genera, and the leaf-mining Agromyza alternantherae Spencer and Disonycha argentinensis, both of large polytypic genera. Disonycha glabrata (F.) may be the closest intrageneric relative of D. argentinensis. Character displacement, also known as ecological shift, may have been the mechanism that led to the divergent host-plant spectra of these two flea beetles. Disonycha argentinensis is a more specialized suppressant of terrestrial alligatorweed and should be a more universally effective biocontrol agent than native North American/), xanthomelas (Dalman) andD. collata (F.), each of which has a broad host-plant spectrum and is an ecological nonanalog of Z>. argentinensis. The mechanism of character displacement (ecological shift) provides a basis for possible utilization of exotic ecological homologs for weed control. As an alternative to competitive displacement, character displacement could result in coexistence through division of the niche and lead to more effective suppression by both insects because of increased specialization. However, such a process may drive the taxon cycle, and advancement along the cycle could lead to less competitive advantage of the biotic agent in time. KEYWORDS: Agasiclesy spp., alligRtorweed, AltevTianthera spp., biogeography, biological control, character displacement, coevolution, Disonycha spp., ecological shift, environment, extrinsic coevolution, evolution, flea beetles, host specificity, intrinsic coevolution, morphological variation, normal bivariate ellipses, phenoclines, polytypic species, semispecies, superspecies, taxon cycle. ACKNOWLEDGMENTS

The field studies on which this work is based were carried out in South America during 1960, 1961, and 1962 and were sponsored by the U.S. Army Corps of Engineers. Travel expenses for an extended trip to South America in 1975 were also provided by the Corps of Engineers. A shorter trip into Colombia in 1970 was made jointly with a field party headed by H. F. Howden of Carleton University. The success of these extensive field studies was made possible by the cooperation and wholehearted support of numerous individuals along the route of the itinerary and by specialists at the Smithsonian Institution and the Systematic Entomology Laboratory, U.S. Department of Agriculture. The basic information gleaned from the herbaria that one of the writers (G.B.V.) visited to examine Altemanthera and related plants was invaluable. These herbaria, in order of initial visit, are U.S. National Herbarium, Washing- ton, D.C.; Imperial College of Tropical Agriculture, Trinidad, West Indies; Jar- dim Botánico, Rio de Janeiro; Museu Nacional, Universidad do Brasil, Rio de Janeiro; Herbario Anchieta, Sao Leopoldo, Brazil; Instituto de Botánica Darwinion, San Isidro, Argentina; Herbario "Barbosa Rodrigues," Itajaí, Brazil; Agricultural Experiment Station, Mon Repos, Georgetown, Guyana; Instituto de Botánica, Buenos Aires; Universidad de Bahia, Salvador, Brazil; Museo de Historia Natural de Montevideo; and Museo de Historia Natural '^Janvier Prado," Lima. The U.S. National Herbarium, one of the five largest herbaria in the world, is an especially rich store of information, most of it unpublished; the field study drew heavily upon it for_ guidance. Similarly, the Chrysomelidae collections of the Department of Entomology, Smithsonian Institution, were a rich source of study material and geographic records of flea beetles. The remarkable, if not unique, representation of larval Chrysomelidae in those collections was of obvious use in this study. Also, we had access to the important South American collections in the Carnegie Museum, Pittsburgh, Pa., and the American Museum of Natural History. Considering the magnitude of their contribution to this undertaking, we express special appreciation to the following biologists: First and foremost has been Lyman B. Smith, U.S. National Herbarium. In order of contact have been Fred A. Bennett, Commonwealth Institute of Biological Control; the late B. Rambo, Colegio Anchieta, Porto Alegre; Angel Lulio Cabrera, Museo de La Plata; Arturo Ragonese and Victor Milano, Instituto de Botánica, I.N.T. A. (Instituto Nacional de Tecnología Agropecuaria, Argentina); Florentino Rial Alberti, Centro Nacional de Investigaciones Agropecuarias, I.N.T.A.; José Candido Carvalho, Museu Na- cional do Brasil; J. S. Moure, Universidad do Paraná; Raulino Reitz, Herbario "Barbosa Rodrigues"; the late W. A. Egler, Museu Paraense Emilio Goeldi; Mario Honda, Djalmo Batista, and W. Antonio Rodrigues, Instituto Nacional Pesquisas da Amazonia; Philip Chan Choong, Department of Agriculture, British Guiana; the late James K. Holloway and Richard E. White, U.S. Department of Agricul- ture; Roberto G. Mallo and Irma S. Crouzel, Instituto de Patología Vegetal, I.N.T.A.; M. J. Viana, Museo Argentino de Ciencias Naturales; Santiago Laserre and Guillermo R. A. Jeckelne, Estación Experimental, Misiones Province, I.N.T.A.; Melquíades Pinto Paiva, Estaciáo de Biología Marinha, Fortaleza, Brazil; the late Jan Bechyné, Museu Paraense Emilio Goeldi; the late Ira S. Nelson, University of Southwestern Louisiana; B. J. Selman, The University, Newcastle-Upon-Tyne; A. Leal Costa, Universidad de Bahia; Heber Sugo, Uni- versidad de la República, Montevideo; O. Vargas, Estación Experimental de Tingo María; Luis Alberto Alvarez, Ministerio de Agricultura y Ganadería, Paraguay; Alberto Burela, Estación Experimental de Saavedra, Santa Cruz, Bolivia; José Villacis S., Instituto Nacional Investigaciones Agropecuarias, Ecuador; Paul J. Spangler, Smithsonian Institution; Troels M. Pedersen, Estan- cia Santa Teresa, Corrientes Province, Argentina; H. A. Cordo, Biological Con- trol of Weeds Research Laboratory, U.S. Department of Agriculture, Buenos Aires; and Paul C. Quimby, Jr., Southern Weed Science Laboratory, U.S. De- partment of Agriculture. We also express appreciation to the late Marvin Carter, U.S. Operations Mission to Paraguay; Quentin R. Bates and Eduardo Descalzo, Embassy of the United States, Buenos Aires; Cecilia Zarur, Instituto Brasiliera Geographia e Estatistica; Jorge Ferreira, Fundaçâo Brasil Central; Leon Yallouz, Office of the U.S. Agricultural Attaché, Rio de Janeiro; Ronaldo de Souza Vale, Instituto do Acucar e do Alcool; and M. H. Moynihan and Gloria Maggiori, Smithsonian Tropical Research Institute, Canal Zone. In addition, we are grateful to the librarians of the Smithsonian Institution and to the catalogers of the Systematic Entomology Laboratory, U.S. Department of Agriculture, who produced over the years a remarkable card index of systematic literature on Chrysomelidae. Over the years, we have been fortunate to have carried out these studies under the direction of W. H. Anderson, Paul W. Oman, R. I. Sailer, R. H. Foote, C. W. Sabrosky, J. M. Kingsolver, C. R. Swanson, and K. E. Frick. About three-fourths of the work reported in this bulletin was carried out at the Systematic Entomology Laboratory, U.S. Department of Agriculture. The remainder of the work was done at the Southern Weed Science Laboratory, U.S. Department of Agriculture. In March 1972, R. I. Sailer urged that a shorter paper be extracted from a large manuscript entitled "Alligatorweed, Related Amaranths, and Their Biotic Sup- pressants in the Americas." This bulletin is largely a result ofthat suggestion. As already indicated, since 1972 much clarifying additional information has come together both from the literature and from the work done with P. C. Quimby, Jr., S. H. Kay, and H. A. Cordo. For critical review of an early version of the manuscript, we are indebted to D. H. Janzen, University of Michigan, and to J. R. Coulson, J. M. Kingsolver, and D. M. Maddox of the U.S. Department of Agriculture. P. C. Quimby, Jr., S. H. Kay, and H. A. Cordo have kindly permitted us to make citations from manuscripts in preparation. For frank and incisive review of the final version of the manuscript, we are indebted to Suzanne Batra and R. D. Gordon, U.S. Department of Agricul- ture, and especially to H. A. Hespenheide, Department of Biology, University of California, Los Angeles. INTRODUCTION

Alligatorweed, Alternanthera philoxeroides, of and alligatorweed and related amaranths are the the Amaranthaceae, is indigenous to South America subjects of this bulletin. but has been introduced into the Southern United It became evident that A. hygrophila and the States, Puerto Rico/ India, Southeast Asia (Scul- other vittate species of Agasicles have evolved ex- thorpe 1967),2 and Australia.^ In all of these places ternal lock-and-key genitalia that serve to differen- it has become an economically important aquatic tiate the species, as shown in figures 2-5 (Selman pest. In preparation for biological control of this and Vogt 1971). These features, together with less weed, Vogt carried out extensive field studies on conspicuous differences in the uncleared aedeagi alligatorweed and various related amaranths and (figs. 27^0), indicate that these populations are their insect predators in South America during reproductively isolated and are correctly recog- 1960, 1961, and 1962. He made additional field nized as species. However, the wide-ranging and studies in South America in 1970 and again in 1975, irregularly variable A^asicies opaca (figs. 6 and 9) when Hugo A. Cordo joined him in southern Brazil, shows little or no appreciable differentiation of Argentina, and Paraguay. Vogt made limited field either the external lock-and-key genitalia or the studies of related amaranths on various trips into uncleared aedeagi. Additionally, facts about dis- the Southern United States, Mexico, and Panama tribution, biology, and morphology obtained between 1965 and 1971. With P. C. Quimby, Jr., and during the study pointed to evolutionary relation- S. H. Kay, he made extensive field studies in the ships between Agasicles and certain species of Southern United States from 1972 through 1977.^ Disonycha and to relationships among some of the During these trips, more than 90 species of insects plant species and also to an intrinsic coevolution- were found affecting alligatorweed. Of the four ary relation between the insects and their hosts. South American insects recommended as control Evidence of such relationships is discussed in the agents, three have been introduced into the South- first part of this bulletin, leading up to proposed em United States and are successfully combating evolutionary dendrograms for the flea beetles and alligatorweed (Maddox et al. 1971; Brown and plants, and a coevolutionary course is suggested in Spencer 1973; Blackburn and Burden 1972; Vogt the second part. et al. 1975; Spencer and Coulson 1976; Coulson Because of the apparent relationship between 1977). Agasicles hygrophila is one of these insects. flea beetle form and host-plant-stem diameter, This flea beetle and related disonychine species Vogtes study included measurements of the internode lengths and stem diameters of 145 specimens ^C. F. Zeiger, personal communication, 23 Oct. 1975. of alligatorweed and two closely related amphibious ^"Literature Cited" begins on p. 133. amaranths. All are indigenous South American ^K. E. Harley, personal communication, 9 Sept. 1976. species, principally of the alluvial lands east of the ^Findings of these widespread field studies are reported in Andes. These plants are the only known hosts of the detail in manuscripts in various stages of preparation. They are: (1) G. B. Vogt, P. C. Quimby, Jr., and S. H. Kay, "Alligator- five species of Agasicles, and with three terrestrial weed, Related Amaranths, and Their Biotic Suppres- species of Alternanthera y they are the only known sants in the Americas"; (2) G. B. Vogt, P. C. Quimby, Jr., and hosts of the closest extrageneric relative of S. H. Kay, "Field Studies of Flea Beetles, Host Plants, and Le- AgasicleSy Disonycha argentinensis (fig. 1) (Vogt biine Predator Parasites in the Southern United States"; (3) and Cordo 1976). These six flea beetle species, 314 G. B. Vogt, P. C. Quimby, Jr., and S. H. Kay, "Progress of Bio- logical Control of Alligatorweed in the Lower Mississippi Valley specimens in all, were measured for 22 different Region"; and (4) G. B. Vogt and H. A. Cordo, "Field Studies dimensions of body and appendages. The data on of Flea Beetles, Host Plants, and Lebiine Predator Parasites morphological variation of host plants and insects in South America." are summarized and analyzed in the third part of

1 this bulletin. Their evolutionary and biogeographi- cate the relationship between the mean values for cal meaning, taxonomic utility, and significance in each set of proportions (x to y) in the evolutionary biocontrol of weeds are discussed in the fourth part. course of the flea beetle species, supposing that The purpose of this bulletin in eightfold: first, to they diverged successively from a common terres- present a digest of information on relationships trial ancestral form near Disonycha argentinensis; among the flea beetles and their host plants (most of fifth, to present separately the mean points and this information was derived from natural history normal ellipses for three geographic forms of the collections and from the field studies outlined fasciate Agasicles opaca and consider their tax- above); second, for the three species of amphibious onomic and evolutionary significance; sixth, to re- amaranths, to present the variations in stem size in cast all of these evolutionary relationships in view of terms of normal bivariate ellipses and relate these currently developing concepts of the biogeography to normal bivariate ellipses expressing the varia- of South America; seventh, to examine critically the tions of external character dimensions of the flea possible coevolutionary course in the host plants beetles {Disonycha argentinensis, each of the four that may have diverged simultaneously from exclu- yittate Agasicles species, and the fsisciate Agasicles sively terrestrial plants to become the present-day forms combined under A. opaca); third, to apply amphibious plants; and eighth, from the results, to these ellipses in discriminating taxonomically the make interpretations that are of importance in the five recognized species of Agasicles; fourth, to indi- biocontrol of weeds. RELATIONSHIPS AMONG FLEA BEETLES AND THEIR HOST PLANTS

Some Host-Plant Characteristics cant divergence has been recognized between these two groups, but not all botanists recognize A. has- Except possibly Alternanthera maritima in sleriana as distinct from alligatorweed because no southern Florida, there is no species of this genus demonstrable differences in flower structures be- indigenous to the United States. However, closely tween the two plants have been found. related Philoxerus vermicularis is probably indig- Each of these species grows in a range of habitats enous along the beaches of the Gulf Coast States from mesophytic terrestrial to aquatic. Most plants (Small 1933; Correll and Johnston 1970). The am- are amphibious to the extent of being able to with- phibious amaranths constitute less than 5 percent of stand at least partial drying of the habitat for the estimated 120 species oí Alternanthera known extended periods. Many plants root on banks and from South America and the estimated 170 species shallow bottoms, or often, especially in the case of known from North America (the West Indies, Mex- Alternanthera hasslerixina, attach themselves to ico, and Central America) and South America a lagoon bottom by a slender cordlike stem. High combined (Lawrence 1951). Most species are meso- water may completely submerge many plants, phytic or xerophytic; a few are halophytic. In which often refloat if rooted to peaty bottoms of South America, there are three additional species intermittent lagoons. of amphibious amaranths besides alligatorweed, East of the Andes, alligatorweed grows over Alternanthera hassleriana^ Alternanthera sessilisy much of South America in a variety of lagoons and and Alternanthera reineckii, A. reineckii grows ponds and in sluggish to swift-flowing water- along river courses, in seepage areas, and in wet courses. Habitats include ditchbanks, point bars depressions (rain pools) over much of southern along meandering streams and rivers, and margins South America. It is limited to regions of campo along trough and oxbow lagoons, backwaters, and (Roberto M. Klein in Smith and Downs 1972). We distributaries in alluvial plains. In deltas, especially have observed extensive colonies in depressions that of the Paraná River, alligatorweed grows behind a natural levee along the Tebicuary River in ubiquitously in diverse aquatic to subaquatic habi- Paraguay and a small colony in a wet meadow in the tats (Burkart 1957). On higher ground along or near Province of Corrientes.^ These plants were being the Paraná River, often on cultivated land, alliga- used only by flea beetles of the genus Systemi, A torweed frequently grows as a terrestrial plant fifth amphibious amaranth, Alternanthera tetra- with rootlike rhizomes, some appearing like large mera y occurs in Brazil,^ but we have failed to find taproots. Many of these sites are seldom, if ever, this plant; apparently it too occurs in the campos. flooded. In Pedersen's view (cited in footnote 6), According to Engler (1934), alligatorweed and A. those above flood level may depend upon human hassleriana are classified under section I of the activities for establishment, but because alligator- subgenus Telanthera, while A. sessilis, A. reinec- weed does produce viable seed occasionally in kii, and A. tetramera are classified under section I southern South America (Vogt 1973), its establish- (Allaganthera) of the subgenus Eualtemanthera. ment by natural means cannot be ruled out. From this classification it is apparent that a signifi- Alternanthera hassleriana very rarely produces seed and is not known to grow on sites that are free of flooding. Both Alternanthera sessilis and A. er. M. Pedersen showed us our first colony of Alterminthera reineckii normally produce abundant seed, and reineckii in a wet meadow on Estancia Santa Maria, Province of Corrientes, 16 Mar. 1975. both occur as terrestrial plants above the reach of ^T. M. Pedersen, personal communication, 16 Mar. 1975. fluvial floods. A, sessüis has an ecological range similar to that of alligatorweed. From what we have seen of this Pupation of Agasicles Species in plant in the Americas, it may not be an indigenous Host-Plant Stems species. However, in the sub-Andean portion of its There are no host plants other than amphibious range, it is the only amphibious amaranth. The amaranths for the genus Agasicles (Maddox et al. smaller watercourses of this region are deeply 1971; Vogt et aJ.«). A flavone feeding stimulant, shaded by tropical rain forest. Under primeval con- isolated from alligatorweed, is involved in the host ditions, the plant may form colonies only where a specificity of Agasicles hygrophila (Zielske et al. tree fall creates an opening. The range of this 1972). All known species of Agasicles are limited to tropicopolitan species extends into the West Indies, the near-saturation humidities of the subaquatic to Central America, and southern Mexico. It is impor- aquatic habitats of the amphibious amaranths. tant to note that A. sessilis appears to be more Species of Disonycha that attack amphibious closely related to Southeast Asian species (T. M. amaranths are restricted to plants growing on ter- Pederson, cited in footnote 6). restrial sites. These flea beetles are oligophagous The internodes of amphibious amaranths are usu- to near polyphagous. Disonycha argentinensis ally hollow and can thereby provide the flotation (fig. 1), D. eximia, D, coHata, D. xanthomelas, D. needed in some aquatic habitats to keep most glabrata, and several species of the very closely of the foliage above water. The tropicopolitan related genus Phenrica (fig. 8) are known to at- Altemanthera sessilis develops the most slender tack amphibious amaranths. All of these insects stems of the three species that are known hosts of pupate in soil and organic detritus, as do almost disonychine flea beetles in South America. A. has- all of their known terrestrial allies in the Alticinae. sleriumi is the most highly specialized, having de- Soil is not usually readily accessible to aquatic flea cumbent floating stems with conspicuously inflated, beetles, and pupation can take place either on an densely pilose internodes (fig. 7). This species is exposed surface, in a manner suggestive of the adapted and restricted to insolated river lagoons Coccinellidae, or in the moist to wet soil near the that fluctuate in level and even dry up for extended water's edge. Lysathia flavipes of South America periods. The intemode pilosity, both when dry and and Lysathia ludoviciana of North America have when wetted by a film of water, may protect against this facultative behavior. Agasicles pupation, on the aquatic flea beetle Agasicles opaca. the other hand, occurs only inside the host-plant A. obovata is confined to Mexico, Guatemala, and stem, with the prepupal, slightly larger than head- Honduras. Although its flower structure is con- sized entrance hole being sealed with frass (not sidered to be very different from that of A. fécula) and a binder that may include an anal exú- philoxeroides,'' it has the appearance of being a date. However, Maddox (1968) reports that "the North American counterpart of the South American ingested [probably not beyond the foregut] stem indigene. This is probably a coincidence of con- tissue from the entrance hole is masticated and re- vergent evolution. Although they have similar gurgitated to form a plug, and the plug is molded growth habits, A. obovata has a narrower ecological along the perimeter of the hole by using the range than does alligatorweed. pro[thoracic] legs and head. Some tissue used to Along the seacoasts of eastern South America, of form the plug is also derived from the inside the Carribean, and of the Gulf of Mexico are two walls . . . ." species of Philoxerus. These curious halophytic The developing flea beetle inside the stem is well plants are similar in growth habit to alligatorweed. protected from rising waters that result in sub- Just as alligatoweeed is a pioneer plant of newly (Continued on page 10.) deposited silts along freshwater courses, Phi- loxerus is a pioneer along seabeaches. ^. B. Vogt, P. C. Quimby, Jr., and S. H. Kay, "AUigator- weed. Related Amaranths, and Their Biotic Suppressants in the ''L. B. Smith, personal communication, 1 Nov. 1967. Americas" (in preparation).

FIGURES 1-6.—Important specialized South American flea beetles of amphibious amaranths. Dorsal view of female, with more enlarged lateral view of pygidium and propygidium (a) and lateroventral side of abdomen of male (b). 1, Disonycha argentinensis. 2, Agaswles hygrophila. 3, A. connexa. 4, A. interrogationü. 5, A. vittata. 6,A. opaca (lower Amazon River form). Inñgs. 2a-5aand 2b-^b the external genitaHa increase in elaboration, progressing from A. hygrophila through A. vittata, the vittate species. Also, there is greater elaboration in fasciate A. opaca than in A. hygrophila.

FIGURE 7.~-Procumbent floating growth habit of the amphibious amaranth Altemanthera hassleriana, from a lagoon along the Paraguay River. Note the pilose surface of the intemodes and the extremely short, ascending portion of the stem, less than 10 millimeters long. This plant sometimes forms loosely woven floating expanses over lagoons and backwaters in South America. When competing with stands of Ekhhomia crassipes, it develops ascending stems like alligatorweed (see frontispiece). (From Chodatl917.)

FIGURES 8-15.—Two more flea beetles of amphibious amaranths, a coccinellid predator, and disonychine egg masses. 8, One of several species of Phenrica that infest amphibious amaranths on terrestrial sites. 9, Agasicles opaca (Paraguay River form). 10, Coleormgilla qimdrifasciata, a probable mimetic model of the fasciate species of Agasicles (figs. 6 and 9). 11, Egg mass of Dùonychxi argentinensis in soil at base of stem of host plant. 12-15, Egg masses of Agasicles on undersurfaces of leaves of host plant (12, A. hygrophila; 13, A. connexa; 14, A. vittata; 15, A. opaca, Paraguay River form).

1 mm

FIGURES 26-31.—Aedeagi of specialized South American flea beetles of amphibious amaranths. 26, Disonycha argentinensis. 2ÍI, Agasicles hygrophUa. 28, A. connexa. 29, A. interrogationis. 30, A. vittata. 31, A. opaca.

FIGURES 16-25.—Immature stages of disonychine flea beeties and related Chrysomelidae. 16-18, Related larval flea beetles, advanced third instar, lateral view (16, Disonycha argentinensis) 17, A. opaca\ 18, A. hygrophila). 19-20, Head capsule, enlarged to show chaetotaxy, oiAgasix^les hygrophila (19, anterior view; 20, lateral view). 21-25, Various pupal flea beeties and a pupal galerucme. Dorsal view and ventral view (a) of entire insect and more enlarged dorsolateral view (b) of abdominal segments VII, VIII, and IX (21, Düonycha argentinensis] 22, Agasicles hygrophila-, 23, A. opaca-, 2A, Altiva ludovidmimi; 25, Pyrrhxilta (Galermella) mergence of short duration, but death occurs under the last rigid structures to sclerotize in the teneral prolonged submergence. Moreover, it is completely adult. They remain pliable and conform to the con- protected from the ectoparasitic lebiine carabid fines of the stem cavity and therefore do not require beetles, which are major enemies of flea beetles that great reduction in width. Much development of the pupate in the soil, including the aquatic Lysathia vitally important wing muscles and reproductive (closely related to Altica) species that pupate facul- organs occurs after the flea beetle emerges from tatively in wet soil. the stem, thereby filling out the pterothorax and In contrast to an earthen pupal cell that can be the abdomen, which are embraced by the folded but formed to fit the contained insect, the stem- still pliable elytra. in temode cavity may be either too large or too small During or after evolution of the stem intemode for the pupal Agasicles, If it is too large, an inse- into the inflated and greatly enlarged form charac- curely attached pupa could easily fall into a wedged teristic of Alternanthera hassleriana (fig. 7), the position inside the intemode cavity, from which flea beetle larva, pupa, and a.dult became enlarged emergence might be impossible. A secure adhesive and broadened to their forms in Agasicles opaca attaching the prepupal integument to the substrate (figs. 6, 9, 17, and 23). Elytral markings became and a pair of highly modified, T-shaped, giant setae fasciate and orange colored in contrast with the surmounting the abdominal posterior processes of ivory markings of the slender vittate species. The the pupa protect against this eventuality (figs. 22, form and markings of fasciate A. opaca have come 22a, 22b, 23, and 23a). To these setae the larval to resemble superficially a major predator, exuviae are inseparably attached. Coleomegilla quadrifasciata (Coccinellidae) (fig. The anal processes of the Disonycha species and 10). This ladybird beetle may be a mimetic model other Alticinae that pupate in the soil are armed because ladybird beetles are thought to be gener- simply (figs. 21, 21b, 24, and 24b) and insecurely ally distasteful to birds (Hodek 1973). The markings engage the larval exuviae. In the surface-pupating of Agasicles opaca are aposematic, judging by aquatic species of Lysathia^ the setae surmounting Rothschild's (1961) application of the term. the anal processes are noticeably more developed Although they are preyed upon by the same (fig. 24b), and they cling to the larval exuviae more species of coccinellid, the slender vittate species of tightly, but not inseparably as in Agasicles, In the Agasicles show no tendency to mimic their major aquatic surface-pupating galerucine Pyrrhalta predator. Instead, they resemble forms of other (Galerucella) nymphaeae, evolution has pro- rather distantly related genera in the Alticinae as gressed farther and along a different course to pro- well as in the subfamilies Galerucinae and duce a remarkable giant T-shaped seta, developed Chrysomelinae. The significance of the resemb- apparently from fusion and great enlargement lance, which seems to be confined to southern South of the submedian pair of setae of tergite VII in- America, is obscure. We have observed no cohabi- stead of the posterior processes of tergite IX (com- tation of a site by two or more of these forms. But pare fig. 25b with 21b, 22b, and 24b). this condition may not be necessary for the exis- If the stem cavity is too small, the prepupal tence of mimicry (Hespenheide 1973). Agaswles may enlarge it by chewing away, but not Over the sub-Andean portion of its range, ingesting, the pithy walls. However, this enlarge- Agasicles vittata (fig. 5), a rather large vittate and ment may result in sufficient weakening to lodge the mostly sylvan species, is entirely dependent on the stem and kill the enclosed insect. Natural selection slender-stemmed Alternanthera sessilis. How- has, therefore, favored evolution of a slender pupa ever, along streams in tropical rain forest, where (compare fig. 22 with 23 and 21) that is more likely to the only natural openings available for colonization fit inside the stem. Bruch (1906) was first to note are widely separated tree falls, the plant probably this conformation of the pupa. grows to full size before the flea beetle can find it. The dimension most affected by the narrowing As a result, stem diameters available for prepupal process has been the pronotal width. Probably be- entry may commonly approach those of alligator- cause it is narrower than the pronotum, the head weçd during the period of initial attack. But drastic width has been less affected. Also less affected has reduction in diameter occurs in ötems regenerating been the width of the elytra. Elytral width repre- from heavy Agasicles attack. This is also true to a sents maximum body width in the adult (figs. 1-6), comparable degree in the case of alligatorweed, but in the pupa the elytra are folded closely against which is the normal host plant about 800 kilo- the body. In addition, after ecdysis the elytra are meters downstream. No significant size difference

10 in the insect was found between the two zones. in larval and pupal chaetotaxy and adult wing vena- This is remarkable in view of the mortality in tion between Disonycha and the closely related the sub-Andean region, especially of females, from genus Phenrica Bechyné (1959). In Agasicles we the lodging of small-diameter stems at prepupal have noted no basic departures from Disonycha in entry points.® mating behavior or in the patterns of the feeding Except possibly in disturbed situations in the processes of adults and larvae. Plains (Llanos) of Mojos, Bolivia, none of the fas- The egg stages of Agasicles and Disonycha (figs. ciate forms of Agasicles mount the massive attacks 11-15), although distinctive, are very similar, and that the vittate species attain. This difference in the first-instar larvae have the same type of egg suppressive effect is probably because of the hirsute burster. ^1 It is vestigial in the second instar and nonascending stem and floating growth habit of absent in the third. Otherwise, the chaetotaxy of Altemanthera hassleriana. Little or no regenera- the three larval instars is similar. This is true for tive growth of reduced stem diameter that could be various Disonycha species and the four species of restrictive in pupating Agasicles occurs. Also, ex- Agasicles that we have studied. tensive observations in the field show that the fas- The larvae of Agasicles and Disonycha are also ciate species and their host plant occur typically similar (figs. 16-20). Except for the legs and the in insolated lagoons. In contrast, all the vittate ambulatory organ surrounding the anus, the species require either cloud cover and rainfall or chaetotaxy of the head and body is much less promi- forest shade for the high humidity (low evaporation nent in Agasicles than in Disonycha, While the rate) needed for massive attacks that result in the prominent tubercles bearing most body setae are reduced stem diameter of regenerative growth. somewhat reduced in Disonycha argentinensis, as compared with other species of this genus and with species of closely related Phenrica, the tubercles Affinities Between Agasicles have all but disappeared in Agasicles, although the and Disonycha setae persist with few exceptions. This near loss of body tubercles, together with Because of their rather slender metathoracic the reduction of most body setae and possibly also femora, slender prothorax, and general adult body some head setae, facilitates stem entry by the pre- form, species of Agasicles were formerly placed in pupal vittate Agasicles species and their fitting in- the genus Systena, Only recently has a clear rela- side small stems. In contrast, having been freed of tionship between Agasicles and Disonycha been the restriction of smaller stem diameters owing to reported (Selman and Vogt 1971). The affinity is large stems in their host, Altemanthera has- borne out by characteristics of both the adult and sleriana, larval and pupal stages of the fasciate immature stages. Agasicles have become quite thickened medially, The relationship is most evident in similarities in but the tubercles and most setae of the larval body antennal segmentation, in the aedeagi (figs. 26-31), show no development beyond the atrophied state in head capsules, and in metathoracic wing venation found in the other species of Agasicles (fig. 17). This of the adults and in the chaetotaxy of the larvae persistence suggests that the reduction of these (figs. 16-20). The wings and the larval chaetotaxy of larval features is related to the prepupa's drawing Agasicles and Disonycha are almost identical. ^^ its stout body by peristaltic movements through a Marked contrasts and discontinuities in these mor- nearly head-sized entrance hole. Each prepupal phological features are found when Agasicles and Agasicles makes such an entrance into the host- Disonycha are compared with less related Al- plant stem, or, as often occurs in heavy infestations, ticinae, such as species of Oedionychus, Systena, utilizes a hole made earlier by another prepupa. and Altica, and with species of still more distantly The tubercles and their individual prominent related genera of Galerucinae, such as Dinbrotica setae found in Disonycha larvae and prepupae may and Acalymma. There are no important differences have important functions associated with daytime resting places in soil and surface litter and in the ^We found only 3 females (2 of these dead in lodged stems) to 15 formation of earthen pupal cells. Such functions are males and a dead prepupa. ^ojolivet (1959) clearly established the basic phylogenetic importance of wing venation in the Alticinae. Böving (1927) i^Paterson (1930) made earlier studies of the egg burster, and Anderson (1938) provided the basis for our study of lar- using the European chrysomeline Phaedon (Paraphaedon) val chaetotaxy. tumidulus.

11 unnecessary for the Agasicles larvae, which do not Polygonum, respectively) and seal off or partition hide by day or pupate in soil. Apparently as a pro- off a cell usually formed by the intemode walls and tection against high temperatures and low humidity the septa. The seal is composed of plant tissue re- (high evaporation rates), Disonycha argentinensis moved from the stem walls by the mandibles and and most other terrestrial disonychines, as larvae incorporated with anal or oral exudates or both and even as adults, are crepuscular to nocturnal, the (Vogt et al., cited in footnote 12). Also, when pre- insects hiding in loose soil and surface litter by day. pupae of Disonycha and OedionychiLs species enter Since there are no hiding places near the water wet soil, they often form an open-ended cell at the surface and since the humidity is high there, surface. It is sealed by courses of mudlike cement Agaskles adults and larvae do not hide by day. applied successively around the periphery of the The larvae of Disonycha argentinensis and the open end until it is closed. Apparently, mud is Agasicles species feed on the stem surface. How- gathered by the anal end of the body and trans- ever, stem entry by Agasicles prepupae involves ferred to the forelegs and mouthparts for appli- behavioral patterns distinct from stem-surface cation. Anal or oral exudates or both are probably feeding by Disonycha. The biting response of incorporated with the mud. Agasicles is not for the purpose of ingestion and These patterns seem to be consistent with the may be comparable to the response of prepupal behavior of the Agasicles prepupa, which usually D. argentinensis making its way head first into amasses, on the sternum, a small ball of plant tissue the soil. Agasicles prepupae select only stems of by biting several successive courses out of the in- their host plants for entry, other plant stems be- temode wall. Six or more of the small masses of ing avoided. This host-plant specificity proba- plant material, applied successively and peripher- bly is aimed at the special compartmentalized ally, are required to close the head-sized hole (Vogt hollow stem of alligatorweed, a characteristic et al., cited in footnote 12). The mouthparts and not found in other aquatic plants that may cohabit forelegs apply the material, as Maddox (1968) re- with alligatorweed. ports. An oral exúdate seems to be incorporated in This positive, presumably chemotropic response the closure, but our observations failed to rule out to the host plant apparently has a counterpart in addition of an anal exúdate. For comparison, we soil-entering prepupal Alticinae. It appears when note that in various species of the closely related prepupae of species of Altica^ Disonycha^ and Galerucinae and in some Chrysomelinae, prepupae Oedionychus are confined to rearing containers spin a cocoon from the anus. In the more distantly without soil. They will feed again after a day or related Chrysomelidae, a sagrine, Sagra femorata, more of frustrated searching. Soon afterwards they lines its pupal cell with a red to black varnishlike will enter soil when it is provided.^^ Tj^jg evidence anal exúdate. In the Cryptocephalinae and indicates that the response otih^ Agasicles prepupa Chlamisinae, the prepupa seals its larval case of to its host plant for stem entry is a carryover from fecular material with an anal exúdate. In the Cly- the larval stage. But it is without the response to trinae, soil particles are incorporated with fecular ingest beyond the foregut. In the case of the soil- material to form the larval case, which the prepupa entering Alticinae, prepupal feeding is presumably seals with a chalky material exuded anally. In these a survival stratagem, and the plant material passes examples of more distantly related Chrysomelidae, through the enteric tract. the encasing and sealing materials are applied with The complex behavior responsible for plugging the mouthparts and forelegs, and this process may the head-sized entrance hole hy Agasicles prepupae entail addition of oral exudates in some cases. In the also seems to have comparable behavior patterns Curculionidae, some representatives construct coin the soil-entering alticine prepupae. This com- coons of oral exudates (Hypera), while others parability becomes evident when prepupae of utilize anal exudates (Odontopus), Several genera Disonychn collata and Disonycha pennsylvanica of leaf-mining Agrilinae (Buprestidae) spin cocoons are confined to rearing containers without soil. from the anus, and some of these are remarkably Some individuals enter open ends of their hollow- elaborate. Even in the aberrant family Brachypsec- stemmed host plants (in this case alligatorweed and tridae, the prepupa spins a cocoon from the anus. ^^ The pupae of the Agasicles species and 12G. B. Vogt, P. C. Quimby, Jr., and S. H. Kay, "FieldStudies Disonycha argentinensis differ markedly. The re- of Flea Beetles, Host Plants, and Lebiine Predator Parasites in the Southern United States" (in preparation). i^G. B. Vogt, unpublished notes.

12 markable T-shaped terminal abdominal setae of coastal halophytes, Philoxerus species, also appar- Agasicles have abeady been discussed. In addition, ently support no flea beetles, although they are the Agasicles pupa has lost two pairs of setae from hosts of one of the important specialized insects of the disk of the.pronotum and a pair of lateral setae amphibious amaranths, the phycitine moth, Vogtia from each abdominal segment (figs. 21-23). We be- malloi. However, along the beaches of the Gulf of lieve this loss is' a result of the restrictive effects Mexico, P. vermicularis and several Chenopo- of the slender host-plant stem upon the Agasi- deaceae are normal hosts of a galerucine, Eryne- cles pupa. Furthermore, the pupa of Disonycha phala maritima. argentinensis shows no transitional features be- Figures 34 and 35 show the distribution of the five tween other species of its genus and Agasicles, species of Agasicles, Disonycha argentinensis, and Pupae within the genus Agasicles have consis- the species of the closely related genus Phenrica tent chaetotaxy. that are known to attack amphibious amaranths. Table 1 gives .known host plants of these and other Altemanthera-oriented flea beetles. Agasicles is Biogeography of Flea Beetles limited to the humid, mostly alluvial regions east of and Their Host Plants the Andes. We have no record of this genus north of the Equator. All species, as known presently, are The four amphibious amaranths and the related allopatric except the vittate species A. hygrophila halophyte of coastal beaches, Philoxerus, are dis- and the fasciate Paraguay River form of A. opaca. tributed as shown in figures 32 and 33. Excepting Z). argentinensis is mostly coextensive with Philoxerus, the plants occur principally in alluvial Agasicles except that it is absent from all but the lands. The range of Alternanthera hassleriana is southernmost reaches of the Amazon River basin. subtropical to tropical, and is contained within the It also extends beyond the range of Agasicles into limits of the farther ranging alligatorweed. Al- oases of the dry regions east of the Andes and at Sao ligatorweed is centered principally in subtropical to Luis, Maranháo State, Brazil (Costa Lima 1954 and temperate southern South America, with additional Blake 1955). At most of these localities, alligator- important centers along the Brazilian east coast, in weed is known to occur, but three alternative host the upper and middle Amazon basin, and in north- plants are now known for Disonycha argentinensis em South America from Belém to Trinidad. that are not necessarily confined to alluvial lands. Alternanthera sessilis is tropicopolitan and, in Alternanthera paronychioides and A. pungens, South America, it occurs on both sides of the Andes. widespread over much of southern South America Although it overlaps the range of alligatorweed, east of the Andes, are host plants near Santa Cruz, most importantly it occurs as the sole amphibious Bolivia, and Corumbá, Mato Grosso, Brazil. Al- amaranth in the upper Amazon River, adjacent to ternanthera kurziiy widespread in the Chaco and and somewhat within the Andean ranges. A. ses- adjacent regions (Pedersen 1967),.is a host plant in silis is also a host plant of Agasicles interrogationis just a few localities between the Bermejo River and and A. connexa along the narrow littoral of Brazil, Arroya Empedrado along the Paraná and Paraguay where our findings show alligatorweed to be the Rivers. D. argentinensis shares this host plant with major host plant. While Alternanthera sessilis Phenrica, which is the only genus of flea beetle we tends to be a sylvan species, we have no evidence of found on this host north of the Bermejo River (Vogt its occurrence in South America outside areas under and Cordo 1976). some degree of human disturbance. It seems most Phenrica ranges over much of tropical North at home in the eastern Andean foothills. As already America, as well as over all of humid South America stated, Pedersen (cited in footnote 6) considers the except the temperate southern areas. The void in affinities of A. sessilis to be with species of South- this distribution includes the important region of east Asia rather than those of the New World. the lower Paraná River and the Rio de la Plata, Alternanthera obovata, the probable North which is the present stronghold of both D. argen- American counterpart of alligatorweed, ranges tinensis and A. hygrophila, Phenrica is a large from Honduras northward to within 400 kilometers complex of closely related stenophagous species for of Brownsville, Tex. Apparently no specialized flea which we have yet to work out satisfactory identifi- beetles have evolved on this plant because of the cations. The reader must bear in mind that, as cited limited area and diversity of the alluvial lands in- in table 1, the Phenrica of Amaranthus, of Iresine, cluded in its range. The Western-Hemisphere-wide {Continued on page 22. )

13 FIGURE 32.—South American distribution of alligatorweed and Altemanthera hassleriana. The records are from the Instituto Darwinión, U.S. National Herbarium, and other herbaria and from Foster (1948), Smith and Downs (1972), and Vogt et al., cited in footnote 8. (Goode Base Map copyright by The University of Chicago Department of Greography.)

14 FIGURE 33.—Western Hemisphere distribution of the amphibious amaranths Alternanthera sessilis and A. obovata and of the combined halophytic amaranths Philoxerus vermicularis and P. partidacoides. These records are from the U.S. National Herbarium and Vogt et al., dted in footnote 8.

15 FIGURE 34.—South American distribution oîAgasicles species. Vittate species (unshaded): A, A. hygrophila. B, A. connexa. C, A. interrogationis. D, A. vittata. Fasciate A. opaca (shaded): E, Paraguay River form. F, Plains of Mojos form. G, Lower Amazon form. In this study, we sampled and observed Agobíeles at 44 of the 50 localities shown. Of the remaining six records, four (Natal, Ilheus, Santos, and Santa Tomé) are from the University of Paraná collections and from the U.S. National Museum of Natural History. Two (Borba and Rio MixioUo) are cited in Selman and Vogt (1971). (Goode Base Map copyright by The University of Chicago Department of Geography. )

16 o Phenrica spp. # Disonycha argentinensis

I 1 1 0 500 1000 2000 k

FIGURE 35.—Distribution of Disonycha argentinensis and Phenrica species, known herbivores of amphibious amaranths growing on terrestrial sites. These records are from the U.S. National Museum of Natural History, the Carnegie Museum, Costa Lima (1954), Blake (1955), and Vogt et al., cited in footnotes 8 and 12.

17 Table 1.—Known host plants ofAlternanthera-oriented disonychine flea beetles (Disonycha, Phenrica, and Agasicles) andZ). conjuncta, one of many non-A/i^r/ia/irt^w-oriented species

Alternanthera •h ~ ce

Flea beetle -Sol 1 '^^ ^ â • and distribution '^ S^JS Ij I ^ ä % l^i Si -So g:S o a. D. xanthomelas: Northern U.S. and Canada ... + + + + Southern U.S + + + + 4- D. collata: Southern U.S + + + + + Mexico + Colombia D. camposi: Ecuador and Peru ... + D. eximia: Panama Trinidad, West Indies D. glabrata: North America + + South America + D. prolixa + D. argentinensis D. conjuncta + Phenrica spp. : Mexico; Central and South America + + + + A. opaca: Lower Amazon River form ... Plains of Mojos form + Paraguay River form + + A. vittata + + A. hygrophila + A. connexa + + A. interrogationis + + ^Adult orientation only; on this host plant, eggs hatch, but larvae do not develop.

18 • Disonycha collata O D. eximia ^ D. politulq ® D. camposi

Scale —I 1 500 1000 2000 km

FIGURE 36.—Distribution of four closely related indigenous North American and South American species of Disonycha. D. collata, D. eximia, and D. camposi infest terrestrial plants of amphibious amaranths, while D. politula is a related species of semidesert habitats. Closer study may reveal that D. collata as represented here is actually either a superspecies or a polytypic species composed of closely related forms. Records are from the U.S. National Museum of Natural History, Blake (1933), Brimley (1938), Fattig (1948), Wilcox (1954), Kirk a969 and 1970), Balsbaugh and Hayes (1972) and Vogt et al. as cited in footnotes 8 and 12.

19 FIGURE 37.—Distribution of North American Disonycha xanthomelas. Unlike D. collata, this species approaches but does not reach the seacoast anywhere in its range along the Gulf of Mexico. Records are from the U. S. National Museum of Natural History, Blake (1933), Brimley (1938), Fattig (1948), Wilcox (1954), Kirk (1969 and 1970), Balsbaugh and Hayes (1972), and Vogt et al., cited in footnotes 8 and 12. (Goode Base Map copyright by The University of Chicago Department of Geography.)

20 Oí pu Ä

gPQ |) ^ Ë ^ -ES I

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21 of Cyathulüy and ofAltemanthera are distinct from Altemanthera sessilis, and an unidentified one another. Also, within those injurious to Altemanthera species.^* In tropical to subtropical Altemanthera there is a complex of both sympatric forest east of the Andes and in Panama, one or more and allopatricPÄ6nrica species. fasciate Phenrica species attack the Western- The largest Agasicles flea beetles are the forms Hemisphere-wide Iresine diffusa. Further south of fasciate A. opaca. They are coextensive with and into the temperate region, a vittate species, the range of their host plant, Altemanthera Disonycha conjuncta, is specific on this host plant, hassleriana, the largest-stemmed amphibious with no trace ofD. argentinensis being found on it amaranth. However, the smallest species of anywhere. Somewhat similarly, east of the Andes, Agasicles, A. hygrophila, does not occur within the Anmranthus supports two to three vittate species range of Altemanthera sessiliSy the amphibious of Disonycha, except in the upper Amazon Basin, amaranth having the most slender stems. (Compare where species of Phenrica replace them. Again no fig. 34 with figs. 32 and 33.) From Asunción to trace of D. argentinensis is found on this plant any- Resistencia, Province of Chaco, Argentina, the where (Vogt and Cordo 1976). Paraguay River form of Agasicles opaca occasion- From the distribution patterns and host-plant really infests alligatorweed in disturbed situations. lations just given, we conclude that the ancestral We also found it exploiting alligatorweed below forms of Disonycha collata and its vicarious forms, Manaus in the lower Amazon. D. eximia and D. camposi, probably invaded South Figures 36 and 37 show the distribution of five America no earlier than the late Pliocene. Further- Disonychu species indigenous to North America more, because their distribution is limited to the and northern South America. Four infest amphibi- northwestern fringes of South America, the inva- ous amaranths, and the fifth, D. politula, is a re- sion may have occurred after the final major uplift of lated species of semidesert habitats. Table 1 gives the northern Andes. Vanzolini and Williams (1970), host plants of the known Altemanthera-oriented Haffer (1974), and Raven and Axelrod (1975) con- flea beetles. In Panama, D. eximia develops on sider that massive immigration of vertebrates from terrestrial plants ofAltemanthera sessilis and on North America occurred in the late Pliocene after the mesophyte Altemanthera ficoidea. It also at- the Middle American land bridge came into exis- tacks alligatorweed in Trinidad, West Indies. tence. In addition, Haffer (1974) states, "The ex- In the Southern United States, Disonycha col- change of northern and southern nonforest faunas lata develops in nature on various Centrospermae, through northwestern Colombia may never again as follows: Trianthema portulacastrum (Aizo- have been as intensive as toward the end of the aceae); Chenopodium album, spinach, and beet Pliocene prior to the final uplift of the [northern] (Chenopodiaceae); and Acnida, Amaranthus, Ire- Andes and prior to the expansion of tropical low- sine dijfusa, Altemanthera pungens,^^ and alli- land forests." Disonycha collata and its vicarious gatorweed (Amaranthaceae) (Vogt et al., cited in forms may be considered as mostly nonforest footnote 12). Blake (1933) also lists Portulaca (Por- faunal elements. tulacaceae), chickweed (Caryophyllaceae), and The indigenous North American Disonycha lettuce (Compositae). Our studies show that chick- xanthomelas, together with closely related D. col- weed, Stellaria media, may be a host when it grows lata, has been found developing on terrestrial al- as a summer annual in cold latitudes, but not when it ligatorweed, Amaranthus (including Acnida) grows as a winter annual in warm latitudes. In species, Iresine diffusa, Chenopodium album, Mexico, Disonycha collata infests the amphibious beet, and spinach at various locations in the South- amaranth Altemanthera obovata (fig. 33) in low- ern United States (Quimby and Vogt 1974 and Vogt lying terrestrial situations and the mesophyte et al., cited in footnote 12). Blake (1933) includes Iresine diffusa in the uplands. In Colombia, a geo- chickweed, Stellaria media, as a host plant of D. graphical form of D. collata develops on terres- xanthomelas. As with D. collata, our studies indi- trial Altemanthera sessilis (Vogt et al., cited in cate that chickweed is a host in cold climates where footnote 8). West of the Andes in Ecuador and it grows as a summer annual, but not in warm cli- Peru, a closely related species, D. camposi, devel- mates where it is a winter annual. In contrast with ops on Amaranthus, Altemanthera halimifolia.

15G. B. Vogt and H. A. Cordo, 'Tield Studies of Flea Beetles, ^^Altemanthera piiTigens (not A. repens) is established as an Host Plants, and Lebiine Predator Parasites in South America" exotic species in the Southern United States (Pedersen 1967). (in preparation).

22 D. collata, D. xanthomelas does not occur on lated/). prolixa)9inàD. argentinensis are attacked Trianthema portulacastrum, nor will it develop on by specific, highly mimetic, vittate species of ec- this host plant in the laboratory. D, xanthomelas is toparasitic Lebia in South America (Vogt and widespread in Canada and approaches but does not Cordo, cited in footnote 15), but as presently reach the Gulf of Mexico as far south as Victoria, known, no vittate species of Lebia attacks D. glab- Tex. (fig. 37). We have not found Disonycha trian- rata in North America (Vogt et al., cited in footnote guLariSy which is closely related toD. xanthomelas^ 12). This diverse information may indicate that D. in the Southern United States (Vogt et al., cited in glabrata has an older history in South America than footnote 12). They have largely overlapping ranges in North America. except that D. triangularis trends farther west While the perfect transference of the North southwardly. Also, this species seems to be more American Disonycha xanthomelas and D. collata oriented to the Chenopodiaceae, although Blake and the West Indian!), eximia may indicate affinity (1933) lists Amaranthus species as host plants. with D. argentinensis, none of them overlap the The transference of Disonycha collata and D. indigenous South American range of alligatorweed xanthomelas, two indigenous North American flea in Recent time except!), eximia, which attacks this beetles, to alligatorweed in the Southern United plant in Trinidad, West Indies (figs. 32 and 36). States indicates chemical similarity of plants and Possibly the Andes Mountains and the dry climate may be important evidence of an afñnity between across northern South America have been effective Disonycha and Agasicles. Also, we have found barriers to their southward dispersal. We have no Disonycha glabrata adults feeding on alligatorweed evidence of their ancestral forms being involved in at isolated but widespread localities in the Southern the speciation that led to archetypal populations of United States. This is either a transitional trans- Disonycha argentinensis. Possibly some of the ference or a vestige of an old orientation to same factors limiting the southward advance ofD. Alternanthera because this flea beetle does not collata and D. eximia have limited the northern complete its development on this plant (Vogt et al., advance of alligatorweed. On the other hand, we cited in footnote 12). In South America, D. glabrata suspect that the ecologically similar vittate has not been observed to attack alligatorweed or Disonycha glabrata and the ecologically similar fas- any other species of Alternanthera (Vogt and Cordo ciate Phenrica species passed through the northern 1976). This discontinuity in a region rich in Andes prior to the final uplift because of their dis- Alternanthera species could be a manifestation of tribution on both sides of the Andes and far to the an old character displacement involving host ranges south into Argentina, as well as far into North of ancestral forms of Disonycha glabrata, D. argen- America. Also, an old South American history for tinensis, and possibly Phenrica species (see p. 38). Disonycha glabrata may be indicated by the com- However, all of our records of D. glabrata on al- parability between the following disonychine flea ligatorweed in the Southern United States are of beetles and their mimetic and nonmimetic pred- springtime occurrences. Because that region has ators: vittate D. glabrata and D. prolixa and their been extensively surveyed at all seasons, the oc- vittate Lebia predator; D. argentinensis and its currences probably represent host-plant responses vittate Leftia predator; fasciate Phenrica and their of flea beetles enroute from hibernation to their fasciate Lebia predators; the vittate Agasicles normal host plants, Amaranthus (including Ac- and their nonmimetic Coleomegilla predator; and nida) species. Only late summer and fall observa- the fasciate Agasicles and their mimetic Coleo- tions were made in South America. Therefore, megilla predator. these very extensive observations are not strictly Sixty to sixty-three insect species were found to comparable. But if the imperfect orientation of feed and develop on amphibious amaranths in South Disonycha glabrata to alligatorweed is a vestige America (Vogt et al., cited in footnote 8). Of these of an old orientation to Alternanthera, this vittate insects, 11 species are narrowly host specific and species could be .the closest intrageneric relative of are listed in table 2. Their occurrence with amphibi- the vittate D, argentinensis. ous amaranths, especially alligatorweed and its Unlike Disonycha collata and D. xanthomelas, closest relative, is consistent and widespread. The D. glabrata ranges widely over South America and more numerous, less specialized to generalized overlaps much of the range of D. argentinensis species, with the possible exception of Herpe- (Costa Lima 1954 and Blake 1955) (ñgs. 36-38). togramma bipunctalis (Pyraustidae), occur irreg- Both Disonycha glabrata (together with closely re- ularly or only locally. We interpret these patterns

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24 of occurrence as being consistent with the con- tration of the alligatorweed geographic range by the clusions of Connell (1961) and McNaughton and genus, 74.1 percent, is comparable with the pene- Wolf (1970) that different species specialize with tration, 81.6 percent, achieved by the monotypic respect to different environmental parameters. In genus Amynothrips and 81.4 percent achieved by phytophagous species, those that specialize on monotypic Vogtia. These three stenophagous gen- host-plant species become more efficient exploiters era may then be compared with the four species of of those species and therefore more dominant in the polyphagous genera as follows: Disonycha occurrence. At the same time, they may force less argentinensis with 41.4 percent penetration and specialized species (with respect to host species) each of the three agromyzid species with 82.4,19.2, into peripheral specializations which may result in and 23.1 percent penetration. (Disonycha argen- their uneven occurrence and low level of fidelity tinensis is replaced by fasciate species of Phenrica with respect to the specialist's host spectrum. over much of the Amazon Basin.) From table 2 we see that four of the specialized Most of the 60 to 63 insect species of amphibious insects, Disonycha argentinensis and three spe- amaranths are concentrated in the region of the cies in the family Agromyzidae, belong to large, lower Paraguay River, the lower Paraná River, and polyphagous genera. In contrast, two of the re- two great estuaries, the Rio de la Plata and the maining eight species belong to monotypic gen- Guaiba River (region A, fig. 34). In this temperate era, Amynothrips and Vogtiüy that are simply to subtropical region we found 49 to 52 species af- stenophagous. The remaining five species are of fecting alligatorweed and Alternanthera has- AgasicleSy which is entirely oriented to the am- sleriana. Nineteen to twenty species were found phibious amaranths (stenophagous). Unlike feeding on alligatorweed snd Alternanthera sessilis AgasicleSy both Amynothrips and Vogtia have un- in the warmer northeastern extension of this region dergone evolutionary change without speciation. along the craggy east coast of Brazil, the Atlantic Low variability or intensive gene flow or both, to forest region of Müller (1973) (regions B and C, fig. which Haffer (1974) attributes monotypy in numer- 34). To the north, in the region inhabited by the ous genera of South American birds, may account Paraguay River form of Agasicles opaca and infor the monotjrpic character of Amynothrips and cluding the vast wetlands of the Pantanal of the Vogtia, Also, the different levels of speciation upper Paraguay River (region D, fig. 34), we among these unrelated specialized insects may rep- found 21 to 22 species Siñecting Alternanthera has- resent different stages of the taxon cycle, as pos- sleriana and alligatorweed. tulated by Ricklefs and Cox (1973) (see p. 28). As We found only 16 to 17 species of insects affecting compared with Agasiclesy we note that Disonycha amphibious amaranths in the vast Amazon Basin. argentinensis has not split up into taxonomically Whereas the specialized species were well rep- distinguishable forms. Also, it is replaced by fas- resented, the generalized to less specialized species ciate Phenrica species over much of the Amazon were not, owing partly to sampling error. However, Basin (fig. 35). The replacement of vittate dis- in the Lower Basin and Middle Basin, we feel that onychine flea beetles by fasciate forms occurs with the lack of insects is more due to scarcity of am- respect to several wide-ranging South American phibious amaranths, poor development of herba- host plants (Vogt and Cordo 1976). ceous flora as a source of alternative host plants, In table 2, the penetration of the alligatorweed and greater habitat instability resulting from the geographic range by the 11 most specialized species magnitude of the hydrographie flux, which annu- shows a wide range of variation. If the species of ally may attain 20 meters between maximum and Agasicles are excluded, the smallest (19.2 percent) minimum levels at Manaus (Sioli 1975). and the largest (82.4 percent) penetrations are reg- In the Lower Basin and eastern Middle Basin istered by the two very divergent (not phyletic) (northern portion of region E, fig. 34), we found Melanagromyza species, one of which, M. alter- only 7 to 10 species of insects, mostly on Alter- nantheraCy is a leaf miner and the other a gall nanthera hassleriana, but also on A. sessilis and former. The very large range of the leaf miner com- alligatorweed, which are rare plants. In the upper pletely surrounds the restricted range of the gall reaches of the Madeira River, including the vast former. Because the speciation that has occurred in Plains (Llanos) of Mojos (southern half of regign Agasicles is completely oriented to the amphibious E, fig. 34), where the hydrographie flux is much amaranths and has resulted in almost complete less Biïd Alternanthera hxissleriana is widespread, geographic exclusion between the forms, the pene- we found only five species of insects affecting this

25 plant, near Trinidad, Bolivia, Alligatorweed was several specialized agromyzids, and the alliga- rare and limited to disturbed soil in the town. In torweed flea beetles, Disonycha argentinensiSy the western Middle Basin and Upper Basin below Agasicles hygrophila, and A. opaca (Paraguay the smaller tributaries (northeastern extension River form). of region F, fig. 34), we found only nine species As shown in figure 32, we have found no records of insects on alligatorweed and Altemanthera of alligatorweed occurring west of the eastern sessiliSy near Leticia, Colombia. In the Amazo- coastal region of northeastern Brazil except in two nian tributary valleys of the Andean foothills subcoastal montane oases. Serra de Baturité^® and (southeastern portion of region F, fig. 34), we Serra do Tombador (at Jacobina).^'^ Besides, as found only eight species on alligatorweed and shown in figure 34, we have no records of Agasicles Altemanthera sessilis. from anywhere in this region. Our experience at Outside the areas where Agobíeles is known to Fortaleza, Ceará State, and inland, but not as far as occur indigenously, we have the following results of the base of Serra de Baturité, indicates that the insect surveys on amphibious amaranths. In South region is too dry. But within the Amazonian belt of America, the Atlantic watershed north of the Ama- heavy rainfall, in the vicinity of Belem and farther zon Basin yielded only nine species on alliga- northwestwardly along the coast at Georgetown, torweed, in the vicinity of Georgetown and on alligatorweed is common, but again we found no Trinidad, West Indies. The adjacent Caribbean trace of Agasicles even though conditions seemed to watershed to the east yielded only six to seven be generally favorable. Furthermore, we have species on Altemanthera sessilis (Vogt et al., cited found alligatorweed only rarely and no trace at all of in footnote 8). The Pacific watershed west of the the vittate Agasicles species between Belem and Andes and north of Lima yielded only four species Manaus. We conclude that there is a separation on Alternanthera sessilis and the transitional am- in the distribution of alligatorweed across north- phibious amaranth A. halimifolia (Vogt and Cordo, eastern Brazil and a much broader void in the cited in footnote 15). In North America, in Pan- occurrence of Agasicles especially between the ama and Mexico, we found only 7 species on vittate species. Altemanthera sessilis and A. ohovata, while in the Haffer (1969 and 1974, p. 20) indicates that forest, Southern United States, we found 35 species on and presumably appreciable rainfall, formed a nar- alligatorweed. All these insects are generalized to row connection west of northeastern Brazil, be- less generalized species (Vogt et al., cited in foot- tween the forests near the mouth of the Amazon note 8). The comparatively large number found in River and those of southeastern Brazil in the not the Southern United States is due to more exten- very distant past. Generally, Haffer (1974, pp. 145 sive surveys and also reflects the abundance and and 151) and Müller (1973) show no presumed forest dominance of the host plant, which exceeds by far refugia in northeastern Brazil except along the any incidence seen in South America. eastern coast during arid periods of the Pleistocene The greatest concentration of insects affecting (figs. 86 and 87). However, existing mesophytic amphibious amaranths in the alluvial areas of vegetation on Serra de Baturité and Serra do Tom- southern South America is centered in the lower bador suggest that they may have served as refugia Paraná and Paraguay Rivers and associated regions in times more arid than the present. and may be related to a greater overall indigenous There is mounting evidence that in tropical South incidence of the host plants in this vast region of America climatic fluctuation during the Pleistocene wetlands (MacArthur and Wilson 1967; Janzen and early Holocene caused rain forest to alternately 1973). This region has extraordinarily diverse, ex- contract and expand around more than a dozen tensive insolated aquatic and subaquatic habitats. widely distributed refugia of relatively small area. We believe that this diversity may exceed that of Dry savannah separated these refugia during the lower and middle Amazon River and be older geologically (Stose 1950; Russell 1967). The lower ^6Hert)arium of Jardim Botánico de Rio de Janeiro, No. 44427: Paraná and Paraguay Rivers and associated wet- "Baturité, a margem os Rio Cambea 'Condea de cima' Serra lands are probably a more stable habitat (less hy- de Baturité; José Eugenio (S.J.) #539 19-VIII-37 det. Joacim drographie range and a richer herbal flora) and may T.A. Fakis." have been the most important centers for the ra- l'^On 19 Feb. 1962, Prof. Alexandre Leal Costa, Universidade de diation of some insects that feed on amphibious Bahia, presented us with specimens of alligatorweed he had collected 330 kilometers inland from Salvador, at Jacobina, Bahia, 610 amaranths, for example, several ceccidomyiids. meters elevation.

26 periods of minimal rainfall. Many of the rain forests Fossil and other evidence demonstrates clearly rejoined during periods of maximal rainfall. These that numerous plants, such as Nipa species, and oscillations caused vegetational change and faunis- various insects, such as Glossina species, have mi- tic extinctions but also provided the isolation neces- grated far and may no longer occupy their region of sary for numerous animal populations to speciate origin (Good 1953; Smith 1962; Ross 1974; Raven and (Müller 1973; Haffer 1974). Much of the faunistic Axelrod 1975). It is conceivable that a plant species' differentiation in lower categories (subspecific most ancient stronghold can have lost much of its through generic) is considered to have taken place insect fauna because of shrinkage of the area of occu- during the past 800,000 years (late Pleistocene and pancy or unfavorable environmental (e.g., climatic) Holocene)(Hafferl974). change or both. Such a relict area may be faunisti- Thus far, only refugia on terra firma have been cally depauperate as compared with more recent and considered. While Müller (1973) takes up both more favorable (usually larger and more diverse) forested and unforested dispersal centers, he rec- areas of occupation. ognizes no comparable refugia in alluvial lands, Our findings in South America may be partly which encompass most of the habitats of amphibious explained by the proposal of Janzen (1968,1973) and amaranths and the Agasicles species that infest Opler (1974) that a host plant and its phytophage in them. Biotic diversity of South American alluvial continental areas are subject to thé theories of islands remains largely unexplained. Alluvial lands land biogeography (MacArthur and Wilson 1967); must have been subjected to various hydrographie that is, the number of insect species supported by a regimes during the climatic oscillations, and their plant species increases as the host increases in area lower and middle reaches must have been sub- of geographical occurrence, in ecological diversity jected to transgressions of the sea. In the case of of occurrence, and in biomass. However, Opler the lower and middle Amazon River, a magnifi- (1974) notes that "the application of island theory to cent estuary 2,500 kilometers long existed a few the number of species found on host plants is in thousand years ago. Since then, the present allu- opposition to the geologic time theory which holds vial plain has been laid down as a rapidly advancing that the number of insect species now found on host delta (Russell 1967). plants is a function of the age and abundance of the The interglacial seas that apparently engulfed the hosts in geologic time." Additionally, he notes a lower Paraná River up to its confluence with the third theory "that offers an explanation for the vary- Paraguay (Vuilleumier 1971) could have only partly ing numbers and densities of herbivorous insects of extirpated alluvial biota, because of the refugium different host plants. [It] is based upon varying afforded by the Paraguay River and the Pantanal. levels of chemical and physical defenses which have Similarly, during glacial advances, this refugium, as been evolved by plants [to escape insect attack]." A well as the exposed Continental Shelf to the north- fourth theory (Slobodkin and Sanders 1969) relates east, must have enabled survival of most forms as environmental predictability to species diversity. thé climate became colder. The narrow littoral of Under this theory, highly predictable areas allow the Brazilian east coast is considered to be a result for greater species diversity. Such a relationship of late Tertiary and earlier faulting (de Oliveira may be consistent with the greater faunistic diver- 1956; Axelrod 1960). sity of alligatorweed in the basin of the Rio de la Measurement of alluvial fill in the Mississippi Val- Plata as compared with the lower Amazon Basin, ley has reliably established the minimum sea level which we consider to be a less stable environment attained during the last major glaciation as 138 me- for this amphibious amaranth. ters below the present still stand, and this was reached after a major fluctuation in the rise from the Ecological and Evolutionary minimum level reached about 50,000 years ago. It is further considered "that no higher stand of Pleis- Considerations Within tocene sea level exceeded today's stand by more Agasicles than 10 meters" (Russell 1967). This range of glacio-eustacy conceivably could have isolated If the theories of island biogeography (IVIacAr- populations along the narrow littoral of Brazil, thur and Wilson 1967) apply to the host plant and its which in places is walled on the inland side by sheer phytophages on continents, as postulated by Janzen granitic escarpments. In places, these are lapped by (1968, 1973) and Opler (1974), it may be that the the present sea level. stage of speciation is important for judging the po-

27 tential of a biotic agent for weed control, because parasites) has been applied in characterizing and in speciation, at least in its earlier stages, and subdivi- selecting biocontrol agents. Those that have had a sion of geographical range are usually one and the long and close association with a host often do not same process; and this process advances the taxon severely suppress it because of high host-parasite cycle. This cycle expresses the expansion and con- homeostasis, there "having been a selection for re- traction of the geographical range and population sistance in the host and for non-virulence in the density of a species or higher taxonomic category parasite" (Pimentel 1963, 1968; Harris 1973). On (Ricklefs 1973); and Ricklefs and Cox (1972) pos- this basis, Pimentel (1963) urged biocontrol work- tulate for island birds, the "progress of a species ers in their foreign explorations to seek agents in- through the taxon cycle reflects effects of pro- festing hosts related to the target species rather gressively reduced competitive ability caused by than the target species itself. Harris (1973) notes 'counter-evolution' of an island biota to the species further that specialized oligophagous agents more coupled with strong competitive pressure from sub- than generalist polyphagous agents, as a rule, have sequent immigrsLnts.''Agasicles may exemplify this high host-parasite homeostasis and may not be suc- possibility when its speciation is compared with the cessful in biocontrol programs. Pianka (1974) states speciation of other important insect genera that it this way: "Individual organisms with narrow attack alligatorweed. The monotypic genera that tolerance limits, such as highly adapted special- are almost coextensive with alligatorweed in South ists, generally suffer greater losses in fitness due America, Vogtia and Amynothrips (table 2), may to a unit of environmental deterioration than represent stage I of the taxon cycle described by generalized organisms with more flexible require- Ricklefs and Cox (1972). In contrsi&t, Agasicles, with ments, all else being equal." a similar geographic distribution, is divided into five Evolution of host-parasite homeostasis is clearly species that may represent stages II and III of the a coevolutionary process, and later (p. 117), we will taxon cycle. (We will later show that one of these show that evolution of host-parasite homeostasis species is polytypic and that the others belong to can be considered to be counterevolutionary. a superspecies.) From this proposal, we may con- Laboratory studies show that the rare member of sider that Agasicles is the older "immigrant" to the interacting set of species is favored by evolution alligatorweed (the "island"), while Vogtia and apparently because intraspecific competition is re- Amynothrips are the more recent "immigrants." duced, permitting evolution of greater efñciency in Therefore, speciation in Agasicles contrasted with interspecific competition (Ricklefs 1973). Under the the lack of it in Vogtia and Amynothrips may indi- limitations of very finite conditions, laboratory ex- cate a lower level of suppressive capability (lower periments show clearly that the process is geneti- suppressive index) for Agasicles, Moreover, the cally determined, can transpire within the brief fasciate subspecific forms of Agasicles opaca^ by period of a year or two, and can result in little to virtue of being at an earlier stage in their speciation imperceptible outward change in the physical form within the genus, may have a higher suppressive of the organisms involved (Pimentel et al. 1965). On index against alligatorweed than their vittate the other hand, in its advanced stages, the taxon congeners despite greater prevalence of their nor- cycle results in morphological and ecological di- mal host, Altemanthera hassleriana, in South vergence that may attain differences on the species America. However, differences in dispersal ability level. For these changes to occur, geological time is among the specialized alligatorweed insects may be necessary, but the time needed is shorter on geo- important because Ricklefs and Cox (1972) point out graphic islands as compared with the mainland. for some birds, especially the migrating species, Also, as the taxon cycle progresses in island birds, that their dispersal power prevents movement of the ecological niches of the interacting species are some forms through the taxon cycle. likely to change. When this occurs in phytoph- Aside from the counterevolutionary effects that agous biocontrol agents, coevolutionary processes may be involved in its progress, the taxon cycle may be diluted by other evolutionary processes. may, in the case of phytophage systems, be a tax- Later, we will show that progress of Agasicles onomically recognizable form of the evolutionary through the taxon cycle may be driven by coevolu- process that leads to host-parasite or host-predator tionary rather than by counterevolutionary pro- homeostasis (Ricklefs 1973). This result of the coun- cesses. Ricklefs and Cox (1972) note further that teradaptive or genetic feedback mechanism exist- after the taxon attains stage IV of the cycle (en- ing between interacting hosts and predators (or demic to one island and monotypic) increasing rarity

28 may either lead to extinction or provide significant and 27-30). However, we have not found appre- release fi^-om counterevolutionary pressure. If the ciable differentiation in either the external geni- latter occurs, the species may again increase and talia or in the uncleared aedeagi within the begin a new cycle of invasion of the islands. A sem- wide-ranging and variable Agasicles opaca (figs. blance of this process may exist in the subspecific 6, 9, and 31). We conclude that this lack of differ- forms of Agasicles opaca, to be considered later. entiation in reproductive organs indicates a lack The considerations above require a closer examina- of reproductive isolation between populations. tion of the course of speciation in Agasicles. Later, we will consider this contrast between the All five species of Agasicles are remarkably alike vittate and fasciate A^asic/es forms. in their adaptation to the aquatic and subaquatic We note, too, that the lock, confined to the males, habitats of the amphibious amaranths. These adap- could serve as a generic character because it is a tations are both behavioral and structural and in- conspicuous and universal feature in the genus. But volve all the life stages. They are, in the best sense in females, the pygidial key is not sufficiently de- of the word, generic and very likely constitute the veloped in two species (figs. 2 and 3) to be useful base from which radiation of the five forms took taxonomically. If it were unmistakably recognizable place. This differentiation appears to have taken in the females of all species, the lock and key would place at least in its initial phases in geographical qualify as a generic character. Presumably, the isolation (Mayr 1970; Diamond 1973) in two basic enlargement of terminal abdominal segments principal ways. evolved in compensation as the flea beetle became First, there was regional divergence in adapta- more slender in conforming to the host-plant stem. tion to climate, to geographic and ecotypic forms of It evolved simultaneously with the other generic the host plants, and to predators. Some of these characters. Then, the cavernous depression of the adjustments are manifest in insect body size and fifth male sternite and associated differentiation form and in the form of markings, e.g., mimicry of in both sexes probably evolved in the course of re- their principal predator, a coccinellid beetle, by the gional speciation. three forms of Agasicles opaca, the fasciate species. The outline above assumes that an earlier wide- Regional adaptations are also manifest in seasonal ranging species split up into geographical isolates and habitat shifts within species as well as in actual and that the peripheral, more widely divergent habitat divergence among species. For example, forms probably broke off earlier than the proximal withm Agasicles vittata, the Peruvian population is forms. This process "of slow genetic divergence and subject to a less severe dry season than the Bolivian subsequent reproductive isolation of geographically population. The forms of A. opaca, the fasciate separated and differentially adopted races or subspecies, are almost exclusively associated with species (Darwin's 'varieties')" is the orthodox view Alternanthera hassleriana in insolated lagoons, among evolutionists (Dobzhansky 1972), and we il- whereas the vittate species are primarily associated lustrate it in figure 40A. Alternatively, the founder with alligatorweed. Agasicles vittata, A. interro- principle (Mayr 1970; Dobzhansky 1972) could gationiSy and A. connexa, which occur in subtrop- apply. This process stems from the establishment of ical to tropical climates are more active during a new population by one or a few individuals in a seasons with increased cloud cover, as well as in region relatively isolated from the parent popula- the shade of the forest, whereas Agasicles hygro- tion. Initial inbreeding leads to a population with a phila, a temperate to subtropical species, is more changed gene pool that natural selection restruc- active in spring and fall but persists in summer tures under local conditions. Such a process could if shade is available. have occurred in the evolution of the forms of Second, regional speciation required the devel- Agasicles opaca across the topography in the vicin- opment of isolating mechanisms in zones of sec- ity of the interface of the basins of the Paraguay and ondary contact between diverging populations, Amazon Rivers, as well as in the evolution of the particularly in the zones of secondary contact vittate A^asictes species along the rugged littoral of (Mayr 1970; Haffer 1974). This evolution is mani- eastern South America. If so, we believe the se- fest in the remarkably divergent external lock- quence of speciation would have been reversed and-key genitalia (figs. 2-6) and in less conspicuous from that resulting from the orthodox process out- changes in the uncleared aedeagi (figs. 27-31). lined earlier; that is, the proximal forms appeared Differentiation among species is remarkably at- earlier than the distal forms. Compare figure 40B tained in the vittate Agasicles species (figs. 2-5 with figure 40A.

29 There is no evidence in any of the forms of River. Paul J. Spangler,i» in July 1969, found the Agasicles that specialization by resource partition- first example of this sympatry in a pond in disturbed ing has occurred. More specifically, there is no evi- land near Asunción. Vogt and Cordo (cited in foot- dence of division of the habitat in the form of a note 15) found another example in March 1976 along common host plant. As a result, there is parapatry a ditch in the outskirts of the city of Formosa. The and allopatry within the genus. Because the Paraguay River form of A. opaca also attacks al- Agasicles species are phyletically related, because ligatorweed along the shores of the diastrophic the ecological niche of each species is so similar, and (nonalluvial) Ypacaraí Lake; the lake, 20 kilometers because each of the species has such high niche- east of the Paraguay River, is completely free of exploitation potential, adjacent sets of species are Altemanthera hassleriana. In disturbed alluvial ecological homologs (Vogt and Cordo 1976) and are lagoons and ponds in the vicinity of Resistencia, subject to the competitive exclusion principle (Har- Province of Chaco, A. hygrophila is also known to din 1960; Pianka 1974). Each of the four vittate occur. Such occurrences are clear evidence that the species and each of the three fasciate forms of two species are capable of competing at frequency- Agasicles are allopatric to parapatric. Only the dependent levels (Ayala 1972) (see pp. 40 and 126). more widely divergent vittate A, hygrophila and Under primeval conditions, such interspecific Paraguay River form of the fasciate A. opaca have competition may have been either rare or a brief overlapping ranges. Characteristically, all three seasonal phenomenon. Important to these consid- fasciate forms occur on Altemanthera hassleriana erations of population interaction is the impressive in insolated lagoons. Only at a few sites about towns long-distance dispersal capability demonstrated and other human disturbances between Asuncion by Agasicles hygrophila in the Southern United and Resistencia does the Paraguay River form of States. In summer this cold-sensitive insect may Agasicles opaca occur on alligatorweed, and in reach inland more than 300 kilometers from perma- these places A. hygrophila may also occur. We nent population foci near the Gulf of Mexico, ^o In know of no other ecological difference between comparison, the distance from Asunción to Ne- these two sympatric Agasicles species than the cochea in southern Buenos Aires Province (the normal occurrence of the one on Altemanthera southern limit of the range of A. hygrophila) is hassleriana in insolated lagoons and the other about 1,500 kilometers, while the distance from on alligatorweed. 18 Of Schoener's (1974) five Corumbá is 2,300 kilometers. categories, this complementarity of niche dimen- Should the range of A. hygrophila prove to reach sions seems to fit group 1: "Food type and habitat: the Pantanal of Mato Grosso, which is a distinct The tendency for species that overlap in habitat to possibility, one might consider the Paraguay River eat different foods." But the categorization is com- form of A. opaca as representing character dis- plicated by the fact that alligatorweed and placement between A. hygrophila and the A. opaca Altemanthera hassleriana typically occur in differ- form of the Amazon Basin. We do not hold this view, ent habitats. This fact may involve Schoener's however; we consider A^^asic/es hygrophila and A. (1974) developing theory of "feasibility of resource opaca of the Amazon Basin as being too widely partitioning as it relates to particular dimensions." divergent in form, and we consider the Paraguay For our discussion two of his five considerations of River form of A. opaca less widely divergent from dimensions are pertinent. They are: "Habitat di- A. hygrophila than either of the Amazonian forms. mensions are important more often than food-type However, we view character displacement (Brown dimensions, which are important more often than and Wilson 1956; Brown 1964) as a process by which temporal dimensions" and "segregation by food closely related allopatric species may become com- type is more important for animals feeding on food pletely sympatric in geological time within the dic- that is large in relation to their own size than it is for tates of the competitive exclusion principle (see p. animals feeding on relatively small food items." 38). Also, an intensive 2-day search of the vicinity of Agasicles hygrophila and A. opaca occur side by Corumbá, Mato Grosso, in mid-April 1975 revealed side on alligatorweed near the lower Paraguay only moderate numbers of the Paraguay River form

^^On Ilha Careira in the lower Amazon, we also found 2 egg 1 ^Personal communication, 10 Nov. 1970. masses, presumably of Agasicles opaca, placed upon alligator- 20G. B. Vogt, P. C. Quimby, Jr., and S. H. Kay, "Progress of weed in a muddy pasture bordering a lagoon supporting Biological Control of Alligatorweed in the Lower Mississippi Altemanthera hxissleriana and A. opaca (Amazon River form). Valley Region" (in preparation).

30 of A. opaca on Alternanthera hassleriana, with no Alternanthera hassleriana, coupled to their evolu- trace of Agasicles hygrophila being found on the tion of mimicry of a principal predator, a coccinellid less prevalent alligatorweed. beetle which may be considered to be the model. Each of the five Agasicles species is quite clearly To close this section, we note that a refutation of equally specialized for exploitation of its particular the competitive exclusion principle may be consid- host plant in its particular geographic region and ered to be in the results of the genetic feedback or habitat. This probably stems from the similarity counteradaptational experiments utilizing the com- of the basic generic characters, described above petitive interaction of two muscoid flies. Musca (p. 30), of each species. The amount of geographic domestica and Phoenicia sericata, under the very variation among the species indicates the degree finite conditions of the laboratory (Pimentel et al. of geographic divergence or derivation among the 1965). However, sinceM. domestica andP. sericata species. Thus, speciation in Agasicles has resulted are distantly related, they are ecological analogs or primarily in geographic specialization rather than in nonanalogs (Vogt and Cordo 1975); and we hold to change in host plant or in specialization on different the view that the competitive exclusion principle plant parts. Adaptive changes yf\i\im Agasicles as will not have been refuted until comparable results the taxon cycle progressed have been minor, except are obtained utilizing a competitive interaction be- possibly the adaptation to the more specialized am- tween two very closely related ecological homologs phibious amaranth Alternanthera hassleriana. such as Agasicles hygrophila and A. connexa. Such There is no evidence of any one form oi Agasicles results in the case of this example, at least, seem gaining a competitive edge over another form ex- theoretically impossible because these two geo- cept in the case of overlapping A. hygrophila and graphically exclusive species are probably optimally the Paraguay River form of A. opaca. There is no adapted to two slightly different climatic ranges. evidence of Agasicles evolving into a new niche to Even so, an intermediate simulated climatic regime avoid competition except possibly the adaptation might be adjusted to be equally suboptimal for each of the fasciate forms to the more specialized of the competitors and provide valid results.

31 PROPOSED EVOLUTIONARY DENDROGRAMS FOR FLEA BEETLES AND THEIR HOST PLANTS

Suggested Coevolutionary adaptations to cope with the aquatic environment, Course possibly including prepupal stem entry. However, those entering oversized or undersized stems fail The suggested evolutionary relationships of the to survive. flea beetle and plant species are presented in figures Initial stem entry must have been by way of exist- 39 and 40. The ancestral plant is generally terres- ing holes and open ends of severed stems and then trial at point 1 and amphibious at 2 (fig. 39). The by holes made large enough to enable passage of the hollow compartmentalized stem must have existed fleshy tubercles and erect spatulate setae of the when Agasicles and its ancestral forms appeared ancestral Disonycha-like larva. The large holes after having diverged from Disonycha argentinen- probably were plugged, judging by the behavior of sis and its ancestral forms, presumably between existing soil-pupating species of Disonycha (p. 12). points 1 and 2. We do not know the relationship of As natural selection reduced the size of the tuber- Altemanthera sessüis (suhgenus Alaganthera) and cles and setae, the making of smaller entrance holes of A. obovata to the evolutionary line leading to evolved, causing less lodging of smaller stems and alligatorweed (subgenus Telanthera). As stated less flea beetle mortality. The making of the en- earlier, Pedersen (cited in footnote 6) considers trance hole must have involved extensions of Altemanthera sessilis to have affinities with larval responses into the prepupal stage. These Southeast Asian species. The Salvador, Bahia, form include the positive chemotropic response to the of alligatorweed is apparently a remarkable host plant with the biting response, but without localized dimorphic form in which almost half of the the response to ingest beyond the foregut. population has stems bristling with erect hairs and For all sew en Agasicles forms, there is no evidence most of the other half has glabrous stems. A. has- of divergence in tropic responses to plants. All sleriana is regarded by some botanists as an forms apparently are host-plant interchangeable ecotypic (more hydrophytic form) of alligatorweed. within the amphibious amaranths. However, the However, the two forms occur side by side in dis- Agasicles forms sort out geographically and by hab- turbed sites. At point 3, inflated internodes are well itat in accordance with their adaptations. As a re- developed. sult, no species is known to attack, in nature, more It may be that the alternative host plants of than one or two species of amphibious amaranths. Disonychxi argentinensis are more recent orienta- Our records show that, in the field, the Para- tions. But if alternative host plants corresponding guay River form of Agasicles opaca and A. hygro- to Alterminthera kurzii, A. paronychioides, and phila develop in both Altemanthera hassleriana A. pungens existed at point A (fig. 40), colonies of and alligatorweed and that Agasicles vittata, A. the ancestral alligatorweed may have been neces- interrogationis, and A. connexa develop on both sarily isolated from their congeners in order for the Altemanthera sessilis and alligatorweed. Also, evolutionary course to proceed. We assume such no-choice testing shows that Agasicles hygrophila isolation as was needed existed at point A for both adults feed only sparingly on cut stem ends of the ancestral terrestrial alligatorweed and its flea Altemanthera paronychioides and A. pungens, beetle. At that point, larvae had prominent setifer- with no perceptible development (Vogt and Cordo, ous tubercles, pupation was in the soil, and adults cited in footnote 15). From these findings, it seems had a broad, short prothorax. But at point B, the that Agasicles, in adapting to an aquatic environ- host plant is beginning to develop amphibious ment, has been forced by natural selection to relin- tendencies, and the flea beetle begins to develop quish any terrestrial host-plant species it might

32 have had even when such plants are closely related Supporting this proposal is the more general host- to amphibious amaranths. As already noted, am- plant range within Alternanthera exhibited by phibious amaranths are plants of heterogeneous re- Disonycha argentinensis as compared with the lim- lationship, since Alternanthera sessilis and A. rein- ited range of amphibious Alternanthera open to eckii are members of a subgenus apart from al- Agasicles. However, we are intrigued by the fact ligatorweed and A. hassleHana, which are truly thsiAgasicles species are attracted to host plants in closely related. water, wheresiBAltemanthera-oñented Disonycha D. M. Maddox^i has suggested that a special hy- species normally avoid plants in water. Both re- groreceptor system may have evolved mAgasix^les, sponses are remarkably clear-cut in the field. This contrast causes us to consider the possible evolution of opposite responses for a homologous receptor. 2iPersonal communication, 20 Apr. 1973. In the evolutionary course there could have been

Divergence

FIGURE 39.-Dendrogram of estimated evolutionary courses of four species of amphibious amaranths from a presumably terrestrial ancestral form. A. opaca A. opaca / # ..o^ /

Convergence Convergence

rJ!;;;^ f u? T^""' of estimated evoluüomrycovorse of Düonyclmarventimmü ^náñwe Agaskles species from an PLW^S™ resembhng D. argentimmü. Three geographic forms of A. opaca are indicated. A, Assuming the splitup of an earlier, wide-ranging species. B, Assuming speciation occurred by the founder principle (see p 29) a continuum of response intensity either way. A At point C, prepupal stem entry is obligatory, special hygroreceptor system may not necessar- T-shaped posterior processes are fully evolved in ily be involved. the pupae, reduction of larval setiferous tubercles is Not far beyond point B (fig. 40) the ancestral form nearly complete, and development of hydrofiige of Disonycha argentinensis diverges from that of pubescence and narrowing of the prothorax and Agasicles and then undergoes some convergence elytra in adults are complete. With adaptation to entailing readaptation toward a more terrestrial the aquatic environment highly developed, radia- habitat, while the ancestral form of Agasicles con- tion of the allopatric forms occurs in close succes- tinues to adapt to the aquatic portion of the host sion. At point D, as the host plant develops the plant's ecological range. If alternative host plants inflated intern ode, the ancestral form of Agasicles existed, the divergence would have occurred at an opaca develops a large, broad, more convex form earlier point in the lineage in order not to require and orange fasciate markings. The three forms of the convergent phase in the evolution of the ances- the Paraguay and the Amazon Basins diverge. tral form oí Disonycha argentinensis. Under this All the vittate species of Agasicles show a ten- condition, the convergent phase might be tan- dency for reduction and interruption of the Li- tamount to divergence between that lineage and shaped ivory-colored markings. This tendency the one attached to alternative host plants and is most pronounced in A. hygrophila and least ancestral alligatorweed away from the zone of iso- pronounced in A. vittata. Figures 42-44 show lation. This complication is not indicated by exist- representative variation in the markings of A. hy- ing species. Also, as compared with Agasicles, grophila. There is no evidence in these and many Disonycha argentinensis has not split up into tax- others of any lateral extension of the interrupted onomically distinguishable forms (see p. 25). markings to form fasciae, such as occurs in the fas- This contrast seems to be related to the interac- ciate species of Agasicles. The greater tendency of tion between the host stem and flea beetle. A. hygrophila to have interrupted markings indi-

34 es

FIGURES 41-44.—Variation in elytral markings oíAgasicles hygrophila. Figure 41 is an aberrant variant (Montevideo, Uruguay). Each group of 3 variants represents apercentage of the sample of 87 females and males as follows: 40 percent (fig. 42), 50 percent (fig. 43), and 10 percent (fig. 44). cates affinity with the forms of fasciate A. opaca to existing species. However, the more fragmen- (compare ñgs. 41^4 with fig. 61). tary fossil record of phytophagous Coleóptera Thus is estimated a course of interactive evolu- indicates some comparability in evolutionary prog- tion of a distinct genus of aquatic flea beetles and a ress. From North American Miocene deposits, group of closely related amphibious host plants. The Wickham (1920) and Kurd et al. (1962) list the mod- ancestral forms of both the host plants and of their ern chrysomelid genera Trirhabda, Pyrrhalta dependent flea beetles probably were terrestrial. {Galerucella), Diabrotica, Luperodes, Altica, and Alternatively, or at least in part, the evolution of Sysiena. Almost certainly Disonycha existed at Agasicles and Disonycha argentinensis could have that time. None of the 11 species listed is recent occurred after the host plants had completed most (Wickham 1920). of their evolution. This alternative would be more It may be that Disonycha has an older history in in accordance with the view that much plant evolu- North America than in South America because tion may have been accomplished before ancestral there are species in North America, such as forms of recent insects became attached to them Disonycha collata, D. xanthomelas, and D. trian- (Jermy 1976). According to Axelrod (1960), the fos- gularis, that have relatively generalized host sil record shows that older Tertiary plants can be ranges and may therefore be more primitive. Also, placed in existing genera and may even be similar a North American aquatic disonychine counterpart

35 to Agasicles may be Disonycha pennsylvanica and their development to terrestrial onagraceous hosts closely related forms. This group of species is such as Oenothera and Gaura. Altica litigata of characterized by costate elytra and is restricted to North America and various Altica species of South the Polygonaceae in subaquatic to aquatic habitats America are transitional in adaptation, developing (Wilcox 1954; Blake 1955; Balsbaugh and Hays 1972; on both amphibious and aquatic species of Lud- Vogt et al, cited in footnotes 12 and 15). The group wigia. Moreover, Altica litigata commonly de- ranges from Canada to Argentina, but it may be less velops on terrestrial Oenothera biennis (Vogt et al., obligatorily aquatic in South America. Besides cited in footnote 12). Disonycha pennsylvanica, Blake (1933, 1955) lists The aquatic Lysathia resort to surface pupation five closely related species from North America and when mud or some other soft, pliable substrate is four other species from South America, including not available for entry. The stems of Ludwigia, D. hicarinata, which we have observed at several with their alternate leaf arrangement and lack of widespread sites in Argentina. Unlike terrestrial compartmentalized hollow stems, may not lend Disonycha, this group of species has fine hydrofuge themselves to prepupal stem entry, thus account- pubescence on its ventral surfaces. However, pupa- ing for the comparatively limited divergence be- tion normally takes place in wet duff and detritus tween the aquatic Lysathia and the terrestrial to near the margins of inundated areas. As prepupae, amphibious Altica species. There have been diver- D. pennsylvanica will also enter existing openings gences, however, such as development of more in hollow stems of its host plant, as already cited. highly specialized hydrofuge pubescence in the Although the D. pennsylvanica group is composed adult and more robust and adhering posterior pro- of somewhat more slender species than most other cesses in the pupa of aquatic species. But there has disonychines, the prothorax has not been narrowed been no lateral restriction of body imposed by and modified as in Agasicles (Vogt et al., cited in a host-plant stem and, consequently, no compen- footnote 12). We believe that the aquatic di- sating increase in body length, with concomitant sonychines of the Polygonaceae may be as old or development of an enlarged and sexually dimorphic older than Agasicles. They probably would be as pygidium, a narrowed but elongated prothorax, strikingly distinct as Agasicles had they come into and other structural changes that seem to have interaction with their host-plant stem. Even though occurred in Agasicles in interactive evolution they are adapted to the aquatic habitat, we do not with the stem diameter of the host plant. consider the Disonycha with costate elytra as close extrageneric relatives oí Agasicles, as much because of their consistent feeding relationship Alternatives to Coevolution with the Polygonaceae as because of their structural divergences. Hering (1951) describes the occurrence of dis- For comparison with Agasicles, there is another junctions in host-plant spectra of certain leaf- possible example of interactive evolution of a group mining insects that occur when a more or less of flea beetles that may have occurred as its host distantly related plant becomes either acceptable plants became aquatic from terrestrial ancestral or seasonally or geographically available as a new forms. The divergence between the plants has been host. In view of this phenomenon there is need to sufficientfor water primroses, Luduoigia species, to consider further the recent transfer of indigenous be clearly distinct from terrestrial genera such as North American terrestrial Disonycha collata and Oenothera Sind Gaura. From the inclusive genus D. xanthomelas to alligatorweed. These somewhat Altica, Bechyné (1959) separated a group of very generalized flea beetles may now have an oppor- closely related aquatic flea beetles under the genus tunity to evolve an aquatic form comparable to Lysathia, Lysathia ludoviciana of North America Agasicles, just as the suggested ancestral form near and L. flavipes and related species of South D. argentinensis did in the geological past. Both America, like the species of Agasicles, are spe- North American flea beetles have adapted as effec- cialized allopatric to parapatric vicarious species tive suppressants of terrestrial alligatorweed. Dur- that are ecological homologs of one another. For its ing flooding, adults of D. collata occasionally take development, each is limited to aquatic and am- refuge on floating mats of alligatorweed. We have phibious water primroses, especially L^6d^(;^^^a pep- found the mimetic predator-parasite of Disonycha, loides. In contrast, the terrestrial species, such as Lebia viridipennis, accompanying the temporarily Altica marevagans and A. foliácea, are limited in displaced flea beetles. Such observations have been

36 made in the more northern, temperate latitudes, the coevolutionary process that follows orientation where the introduced Aflfasicies hygrophila may not of an insect species to a new host. For definitive become an important suppressant (Vogt et al., cited studies, we necessarily restrict our definition of in footnote 12). coevolution to ongoing (intrinsic) interactions. The transfer of two North American flea beetles Whenever they can be recognized, we either ex- to an introduced South American host plant consti- clude or identify the extraneous phases. Ehrlich tutes a disjunction in host-plant spectra for two and Raven (1964), however, do not make this dis- moderately generalized species. Earlier, these tinction in their concept of coevolution. Under same flea beetles added introduced chenopodia- this term, they include, with no exceptions indi- ceous beet, spinach, and Chenopodium album to cated, "the stepwise [the steps may be diverse in their host-plant spectra, when formerly they were size] responses on the part of the insect to the evo- restricted to North American species of Amaran- lution of secondary plant substances" and other thaceae and possibly S¿^Ziana species (Caryophyl- phytochemical attributes and structural and me- laceae). In these cases, the plant was brought by chanical characteristics. They include under co- man into the indigenous range of the flea beetles and evolution the new adaptive zones (mostly in the was accepted as a host. The proposed evolutionary form of new host plants) that the stepwise re- history of Agasicles and the biogeography of the sponses open up to the insect under consideration. amaranth-feeding disonychine flea beetles point Also included is the reverse process in which the clearly to the probability of these disjunct host- host plant resists or excludes insects by evolving plant transfers. a new phytochemical or physical protective sys- Disjunction in host-plant range may also evolve in tem. Because the reverse process occurs during an situ between plant and transferring insect. In such ongoing bio tic interaction, we also consider it as be- cases, the transferring insect may undergo genetic ing intrinsically coevolutionary. changes in responses and tolerances and in habitat In host-plant disjunctions (stepwise shifts), al- and nutritional requirements. A more or less dis- though the phytochemical and other changes may tantly related plant may become an acceptable host have occurred passively or coincidentally with re- as a result of coincidental or convergent evolution of spect to the subject insect, these same changes in its phytochemical and other characteristics that at- new host plant could likely have resulted fi:x)m the tract, tolerate, and provide an adequate diet and plant's interaction with other biotic agents having habitat for a transferring more or less specialized, an extended prior history of association with that phytophagous insect. One of us^^ has extensive evi- plant. This complexity is touched on by Ehrlich and dence of this type of disjunction in Neotropical and Raven (1964) and may be the reason for their dis- Nearctic leaf-mining Buprestidae. In some species regard for the extraneous phases that lead to par- the transfer is limited to occasional eggs being ticular coevolutionary processes. They stress the placed on the disjunct host. In other related species importance of considering the coevolution of in- all eggs are placed on the disjunct host, while the sects and plants in the perspective of geological adults feed only on the ancestral hosts. In still other time, emphasizing that there must have been a suc- related species the transfer is complete, with all cession of many and various interactants shifting stages of the insect confined to the disjunct host. from one evolutionary line of plants to another. Transfer of insect species to new plants that are From this it can be seen that for a given evolu- closely related to the ancestral hosts may also occur tionary line of plants, the interaction with a given in the same manner. But such cases are inconspicu- evolutionary line of insects may be relatively ous and require close study for resolution. Analysis brief. However, that same line of insects may con- remains to be done of tens of thousands of rearings tinue on alternate host plants. and field observations that may reveal clear evi- While many wide disjunctions seem to be clearly dence of this process in less disjunct, closely related coincidental, narrow disjunctions in host-plant host plants. spectra probably more often involve essentially The various processes that lead to the formation coevolutionary processes. The close ecological and of a disjunction in host range, whether they be genetic relationships within the plants and within, coevolutionary or not, are extraneous (extrinsic) to the insects may result in such a complex of interactions that recognition of coincidental disjunctions would be impossible. Also, within these interacting ^G. B. Vogt, unpublished studies. guilds of species, oligophagous insects may lose

37 one or more host species only to regain them later. In a similar vein, Janzen (1968) points out: Loss of a host-plant species may occur when plant Island archipelagos are well known for the pro- resistance develops to the point of exclusion. Insect duction of clusters of similar species from single exclusion by host-plant resistance may be aug- founder species. The same thing appears to hap- mented more or less by the advantage gained pen within insect groups, if the plant genus or through changing plant community characteristics, family is regarded as the archipelago. By bridg- or plant defense guilds, as proposed by Atsatt and ing the defensive system of a particular plant species, the insect species may now spread to O'Dowd (1976). Such changes may deflect the other plant species with the same defense system chemotactic and other responses of the subject in- [new adaptive zone] (e.g.. Ehrlich and Raven, sect from the plants in question. The changes may 1964). also increase the pressure of the subject insect's Also, we note the degradation and detoxification predator-parasite complex. As stated earlier (p. of insecticidal canaverine in Dioclea seeds by a 23), the feeding of Disonycha glabrata adults on specialized bruchid as described by Rosenthal et al. alligatorweed, in addition to their feeding on (1977). Additionally, Rothschild (1973) cites numer- normal hosts within Chamissoa and Amaranthus ous examples of disjunct host-plant patterns among (including Acnida), may be either a transitional aposematic insects that sequester toxins present in transference or a vestige of an old orientation the food plant and thereby acquire protection to Al temanthera. against predators. Pharmacophagy orients such in- Also, reduction in stature or near extinction, or sects to "isolated genera of plants from unrelated both, of a host-plant species may cause gaps in plant families which share the same toxic secondary host-plant spectra. Extended geological time may plant substances. . . ." be necessary for this process to take place and for Stepwise coevolutionary patterns and the ability appreciable gaps to appear. But in our time we are of the first organisms entering a new adaptive zone witnessing the demise of the American elm and the to increase its host spectrum and to radiate into American chestnut as older trees. Simultaneously, species groups have prompted Ehrlich and Raven numerous insects are losing important hosts, and (1964) to reject a widely held idea, namely, the some narrowly specialized dependent species are "theoretical picture of a generalized group of becoming extinct. ^^ polyphagous insects from which specialized In applying the theories of island biogeography to oligophagous forms were [are] gradually derived." the host plant and its phytophages on continents, As cogent, far sighted, and far reaching as their Opler (1974) treats narrow to somewhat broader rejection is, it is conceivable that character dis- host-plant disjunctions in the following synthesis: placement (Brown and Wilson 1956; Brown 1964; The relationship discovered between diversity of Mayr 1970), or ecological shift (Schoener 1974), may [lepidopterous] leaf miner guilds and the area of host [oak] occupation should be viewed in an be a means by which the host-plant range of a evolutionary context. Through time, the number of species may be reduced or reduced at the same time leaf miner species feeding upon a given host will that new hosts are added, disjunctly or not. For remain in equilibrium as the area of host occupation example, iiDisonycha glabrata is considered to be changes. The evolution of new species or extinction the closest intrageneric relative ofD. argentinen- of previously existent ones maintains the equilib- sis, we may make the following speculations from rium. By examining the taxonomic affinities and host relationships of extant leaf-miners in Califor- the dendrogram shown in figure 45. Below periods nia, the source area from which new miner species A and B both Dg (Disonycha glabrata and its ances- are acquired by hosts of increasing distributional tral forms) and Da (D. argentinensis and its ances- area can be readily envisioned. The source area tral forms) were closely related allopatric species for new colonists is only rarely some distant ar- having the same host plants, Alternanthera species chipelago (another oak region), but is usually some sympatric host, although it need not be the closest and Chamissoa-Amaranthus species. Within related congener in the taxonomic sense. For ex- period A, the two species became partly sympatric ample, three relatively unrelated oaks of northern and underwent character displacement with re- montane affinities share the three closely related spect to host plant. In the area of overlap, Dg be- members of a single species complex of miners. came partial to Chamissoa-Amaranthus, and Da became partial to Alternanthera, In period B, the ^G. B. Vogt, unpublished notes. overlap of the species expands to completion in

38 Divergence Convergence

FIGURE 45.—Postulated evolutionary course of Disonycha glabrata and its ancestral forms (Dg) and D. argentinensis and its ancestral forms (Da), assuming that these two species are phyletically related. We have not studied the relationships between several vittate species of Disonycha similar in form toD. glabrata. We therefore assume subequal amounts of divergence and convergence with respect to division of host>plant spectrum. But this subequality does not likely apply to change of form. The difference in form between D. glabrata and D. argentinensis could most likely have resulted from divergence in the direction ofD. argentinensis. Symbols Ah through Aoa represent the five species of Agasicles (species 2 through 8 on fig. 40).

South America, and all forms oriented to both fishes that ecological shift can arise from phenotypic Chamissoa-Amaranthus and Alternanthera are (behavioral) plasticity as well as from genetic displaced. Above periods A and B, Dg and Da con- changes (Schoener 1975; Werner and Hall 1977). As tinue to be stenophagous, but on generically distinct yet, we have not clearly identified shifts in host- host plants. They continue to diverge structurally, plant spectra in insects because of phenotypic plas- and Dg may have extended its range into North ticity. However, testing under confinement often America by way of Chamissoa and Amaranthus shows that insects have a somewhat broader host (including Acnida). range than they are known to have in nature. There is evidence from studies of lizards and sun- Because it applies to closely related species that

39 were originally allopatric, character displacement, convergence described by Cody (1973) in birds, or ecological shift, is important in the practice of mostly from the standpoint of flocking behavior. He biological control of weeds whenever one ecological believes that the consumer species involved may be homolog is considered for introduction to compete either closely related (and possibly including ecolog- with another. It may be assumed that the homolog ical homologs) or distantly related (and possibly considered for introduction is the more aggressive including ecological analogs). As compared with re- species. If character displacement results in divi- source abundance when character displacement sion of the host-plant spectrum shared between the (character divergence) applies, the response of two closely related species, in time either biotic character convergence occurs when resources are in agent or both may become increasingly suppressive short supply and cannot support the consumer because such a division in effect initiates an increase species separately. This would mean a single shared in host-plant specialization that may increase effi- host plant or group of host plants instead of two or ciency of host suppression (see p. 25). Conceivably, more separate host plants, each with a different new host plants might be added during or after the consumer species. We believe that, in phytopha- division of the host-plant spectrum. Such extension gous insects, this process could either cause host- of host-plant range might counteract the progress of plant spectra to converge or prevent a host-plant host-plant specialization. Both the reduction and spectrum from diverging. Ecological homologs and the extension processes would be aimed at attain- analogs as described by Vogt and Cordo (1976) may ment of geographical coexistence rather than at be involved in this process. But since weed prob- geographical displacement of one species by the lems do not, as a rule, involve resource scarcity, other. Besides division of host spectrum, character biocontrol workers may seldom become concerned displacement may occur in other ways that result in with this process. increased specialization: by division of the ecological We have considered the process of coevolution as range of the shared host-plant species; by division of well as the coincidental and interactive processes the plant parts of the shared hosts; and by the that result in increases, decreases, and disjunctions development of distinct periodicity on the part of in host-plant spectra. Before proceeding to the next the insects. If character displacement does not section, we need only to briefly mention the impor- occur, one of the homologs may either be displaced tance of specialized insects in determining the com- geographically or become extinct. position of plant communities. We know that exotic We note further that the taxon cycle would prog- plant species such as alligatorweed are aggressive ress as speciation occurred by means of character invaders that often displace all other plants in cer- displacement. At the same time, as Pianka (1974) tain habitats when introduced into regions lacking points out, there would be a shift from r selection to their specialized herbivores. Often, in their native K selection. These two opposing selective forces habitats, such plants are of relatively low incidence, favor respectively the ^V strategists^ organism, sometimes growing as members of mixed com- characterized by high reproductive rates, and the munities. This sparse occurrence is mostly a result "if strategist" organism, which subordinates re- of biotic suppression by specialized organisms, of productive rates to competitive or exploitative effi- which insects are a major component. ciency through specialization. With this background and that given earlier on Conceivably, some previously allopatric, closely biology and biogeography of Agasicles and related related phytophagous species may overlap in range flea beetles and their host plants and with the and still coexist without ecological (including host- dendrograms in mind, we proceed to some quan- plant spectra) division or anatomical division of the titative studies of variation in the five species of shared host plants. We suspect that some of these Agasicles and the related Disonycha argentinensis. species are likely ecological nonhomologs and This presentation provides evidence for the nonanalogs (Vogt and Cordo 1976). Ayala (1972) has evolutionary course of a genus of specialized insects reported density-dependent coexistence in closely interacting with the host-plant stem. We will dis- related saprophytic Drosophila species that may cuss speciation, the possibilities of coevolution, and actually be cryptic (sibling) species. However, pos- the finding of new, fully evolved host plants in the sibly applying in some species may be the character course of migrations.

40 MORPHOLOGICAL VARIATION IN FLEA BEETLES AND THEIR HOST PLANTS

The method described by Kim et al. (1963, 1966) Measurement of Flea Beetles provided the guidelines for much of the method for this study. Modifications are described below. The composition of the flea beetle samples is given in tables A-3 and A-9 (appendix). All speci- Measurement of Plants mens are from elevations near sea level to 120 meters, except those from the Huallaga River, which The composition of the samples of host plants is are from 610 and 640 meters. The specimens were given in table A-1 (appendix). Selection of plants to collected February through May in 1960, 1961, fit herbarium sheets was minimized by trimming 1962, and 1975, except for those â:'om Leticia, Co- large specimens to fit. lombia, collected in June and July 1970. All collec- All specimens are from elevations near sea level tions were by Vogt and his associates in the field, to 95 meters, except those from the Huallaga River except for those taken by Paul J. Spangler at (610 m)and Pucallpa (160 m), Peru. The specimens Luqué, Paraguay, and near Itabuna, Bahia, Brazil, were collected from February through May in 1960, in June 1969. All materials will be deposited in the 1961, and 1962, except for those from Leticia, Co- U.S. National Museum of Natural History. lombia, collected in June and July 1970. Except for Collecting in all cases was done by observation eight specimens numbered 1,462,766 and 2,282,379 rather than by sweep net. In those collections of in the U.S. National Herbarium, all specimens are which only a portion of the specimens was mea- from 30 numbers in Vogt's herbarium within the sured, individuals were picked at random from series 1087 through 2138. All materials will be de- samples previously sorted into female and male posited in the U.S. National Herbarium. groups, but overly teneral and damaged speci- The four plant dimensions used in the analysis are mens were eliminated until the desired number of given in table 3. Measurements were also made of measurable specimens was attained. the stem diameter 80 millimeters from the terminal, We have not exhausted the possible dimensions the stem diameter at the middle of the fifth inter- for measurement of exposed body structures. node from the terminal, and the length of fifth inter- Rather we selected those dimensions which seemed node from the terminal, but these dimensions var- more likely to show a relationship with the host- ied too much to be useful analytical characters. plant stem diameter. We did not make measure- Vogt measured internode and stem lengths by stepping with a pair of dividers set at 10.0 millimeters. The remaining length, if any, was measured Table 3.—^Plant characters analyzed with a 10-centimeter portion of a Keuffel and Esser Number Character Abbreviation (KE) standard meter scale divided in 0.5-millimeter units. Stem diameters were measured directly with 1 Stem diameter at midpoint of inter- Int'nWL the KE scale; the measurements reported here re- node falling within 80 mm of terminal. flect the shrinkage and internode collapse resulting 2 Length of that internode. Int'n L. from pressing and drying specimens. In living 3 Length of ascending stem (from last AscdngL. Altemanthera hassleriana, the maximum inter- rooted node to terminal for lead node diameter is near the middle, but in the other stem). aquatic amaranths, it is at the apex. Data on the 4 Stem diameter at base of ascending Int'n W3. reliability of measurements are given in table A-2. stem.

41 lAW I*- HW-*|

U2W .^PyL |^PyW-*| k-MTL-H

FIGURE 46.—Characters measured in flea beetles. The abbreviations are identified in table 4. ments of the female spermathecae and the male having a 10-millimeter squared area (100 squares). aedeagi. Aside from the technical difficulties in Both of these micrometer reticules were calibrated their measurement, there is the problem of relating with a stage micrometer to two significant figures measurements of the female structures with those for each of the three objectives. The linear mi- of the male. Such measurements, however, would crometer was used for all measurements except for have been more likely diagnostic from the tax- those appreciably exceeding the 5-millimeter Unear onomic standpoint than have those we measured of scale at the given magnification but falling within the exposed body structures. the 10-millimeter squared area. Of the 32 characters measured, 10 were not All specimens were preserved in 75 percent utilized in order to reduce the amount of work. They ethanol and were therefore in a relaxed condition. are length and width of the fifth sternite, apical Each specimen was measured and read for all qual- width of pronotum, lengths of antennal segments 1, itative and meristic characters at one time.^^ This 2, and Sthrough 11, and the width of segment 9. The procedure was necessary to minimize the practical 22 characters analyzed are illustrated in figure 46 problems inherent in measuring and reading rather and listed in table 4. large-sized whole specimens that were oriented as All measurements were made by Vogt, using a needed on a wad of absorbent cotton and moistened stereoscopic microscope equipped with 1 x, 3 x, and 6x objectives and 9x oculars, the left one being fitted with a linear graduated ocular micrometer 5 2^Most of the meristic and qualitative readings will be covered millimeters long, and the right one, with a reticule in a future paper.

42 Table 4.—Insect characters analyzed^

Number Chanuîter Abbreviation Objective Aspect

1 Body length TBL 1 Dorsal. 2 Body width EW 3 Dorsal. 3 Body thickness BTh 1 Lateral. 4 Headlength HL 3 Lateral. 5 Head width HW 3 Dorsal. 6 Interantennal width lAW 6 Dorsal. 7 Interocular width lOW 6 Dorsal. 8 Pronotal length PrL 3 Lateral. 9 Pronotal width PrW 3 Dorsal. 10 Elytral length EL 1 Dorsal. 11 Minimum internal width of elytral "U" UIW 3 Dorsocaudal. 12 Maximum external width of elytral ''U" U2W 3 Dorsocaudal. 13 Pygidial length PyL 3 Lateral. 14 Pygidial width PyW 3 Caudal. 15 Length of metathoradc tibia MTL 3 Anterior. 16 Antennal length AL 1 Dorsal. 17 Length of 3d antennal segment 3AL 6 Dorsal. 18 Length of 4th antennal segment 4AL 6 Dorsal. 19 Length of 5th antennal segment 5AL 6 Dorsal. 20 Length of 6th antennal segment 6AL 6 Dorsal. 21 Length of 7th antennal segment 7AL 6 Dorsal. 22 Width of7th antennal segment 7AW 6 Dorsal. *The characters measured are illustrated in fig. 46.

as needed with 75 percent ethanol in a Syracuse values are: C^x = 0.0344 and Cgx = 0.0170. We have watch glass. Each portion of the insect was care- not corrected the statistics presented in tables A-4 fully maintained on a horizontal plane while be- and A-6—A-8, nor have we corrected the scales of ing measured. the graphs given in figures 50-60. However, we Data on the reliability of the flea beetle measure- have adjusted the scales of the 1977 series of graphs ments are given in table A-4. In connection with (figs. 62-72) so that the phenoclines and normal some of the high coefficients of variation, head ellipses are as nearly equalized in configuration and length (HL) and pygidial length (PyL) each involve size with those of the earlier results as is practica- landmarks that have a contrast in focal plane with ble. We have not made the fine adjustments needed respect to the horizontal axis of the specimen to fully equalize the configurations of the two sets of oriented across the field of the microscope. In the results because of the tedium and time required for case of the maximum external width of the elytral this graphical method. However, the scale values "U" (U2W) and the length of the third antennal given in the more recently prepared charts approx- segment (3AL), it is possible that the three mea- imate the corrected values for the graphs of the surements could have been made inconsistently on earlier set. We feel some students will find it in- the right or left side of the specimen. structive, as we do, having the incorrect data pre- Two sets of measurements of flea beetles were sented. The pictorial aspect of the presentation is made. The larger set was done during 1968-70 and essentially unaffected. We note, though, that the is treated separately from the second, which was mean points in figures 62-72 not central to the three made during 1976-77 to incorporate additional sam- plotted normal ellipses were calculated by non- pling from the surveys made in 1975 in South machine methods, i.e., by slide rule. Although these America. In processing the 1977 data we discovered calculations have been rechecked three times for that Vogt had inadvertently applied incorrect cali- accuracy, close comparison shows there are some bration factors for the 3x and 6x objective mea- minor discrepancies between them and the corre- surements made during 1968-70. The incorrect sponding mean points of the earlier phenoclines calibration factors are 0.0312 and 0.00598, respec- that are based upon Wang 700 output (figs. 50-60). tively, for the 3x and 6x objectives. The correct All phenocline distances utilized in tables 5, 6, and

43 8 through 13 were measured with a 15-centimeter containing 95 percent of the possible points (x^y) section of a Keuffel and Esser standard meter scale from a given population. The size and shape of each divided in 0.5-millimeter units. All measurements ellipse depends on the variances, correlations, and were made on the originals of the indicated graphs. sample size fi-om which the parameters were com- puted. If the variances are small, the ellipse is also small. If the two variances are equal and the corre- Correlation of Characters lation coefficient is near zero, the ellipse becomes a circle; as the correlation coefficient approaches 1, the ellipse degenerates into a straight line. If the Using a Wang 700 programmable electronic cal- sample size is small, the ellipse is large, decreasing culator, J. U. McGuire, Jr., developed and carried with increasing sample size. out a program to reduce the measurement data to It should be stressed that the representation of common terms, obtain the mean and standard de- our sample sets by normal ellipses is strictly a deviation for each of the plant and flea beetle characters, and obtain the corresponding coefficient of scriptive statistical technique. It is thus not intended that the graphs be used for purposes of correlation and the points for each of the corre- statistical inference (i.e., testing hypotheses). In sponding bivariate, normal, 95-percent-tolerance the judgments we have made, the graphs have been ellipses. 25 McGuire conceived the application of the only one of many inputs. normal ellipse. The correlation coefficient is a parameter of the In the graphs, each bivariate normal ellipse is bivariate normal distribution. It is related to the centered on the mean point. For the flea beetle angle that the major axis of the ellipse makes with species, we postulate the same sequence for the the horizontal axis. If the angle is between zero and mean points as we give for Recent time in the den- 90°, the ellipse is inclined to the right and the corre- drogram that hypothetically represents the evolu- lation is positive. If the angle is between 90° and tion of the six forms of flea beetles from a single ancestral form (fig. 40). Therefore, in each graph 120°, the ellipse tips to the left, and the correlation coefficient is negative. Ellipses in parallel alinement (figs. 50-60 and 62-72), we consider the line con- indicate maximal intercharacter correlation, necting the mean points of the species in this whereas ellipses oriented at various angles signify sequence as an evolutionary trend line for the par- low intercharacter correlation. Characters having ticular pair of variables (characters) plotted on the the least intercharacter correlation between the graph. This trend line corresponds to the phenocline of Ross (1974). species tend to be more discriminant and therefore most useful taxonomically. Discrimination is ex- After the correlation of characters in the plants, pressed by the amount of separation or overlap we will consider three different versions of the among the ellipses representative of the species. Disonycha-Agasicles phenocline. We will take up the first version (figs. 50-60) in the next section, "Flea Beetles (Recognized Species)" (p. 49). Next, Plants we will consider the second version (figs. 62-72) in the section "Flea Beetles (Subspecific Forms of The means, standard deviations, and coefficients Agaskles opaca)" (p. 76). Last, under "Proposed of correlation of the four plant-part measurements Trifúrcate Representation for the Phenoclines" (p. taken of Alternanthera philoxeroides, A. has- 103), we will consider the third version (ñgs. 74^4). sleriana, and A. sessilis are given in table A-5. The In the third version, the order of the mean points graphs (figs. 47 and 48) show the corresponding sets is changed. of normal ellipses for the three plant species. In The bivariate normal ellipse encloses the area addition, a few individual points are plotted for certain growth habits for which there was insuffi- 2«Late in this study McGuire reprogramed on a Wang 2200 and cient sampling. corrected a slight error in the Wang 700 program, in which In figure 47, stem size is expressed by length of Ä;=2F2.„_i (n-2M-l) was used instead ofÄ: =2F2.„-i (n-l/n-2). the ascending portion of the stem and its basal We applied the Wang 2200 output in the following graphs (fig- width. It is strikingly clear that the ascending stem ures): 65A (Paraguay River form only), 65B (Plains of Mojos of floating decumbent A. hassleriana is remarkably form only), and 66, A and B (all forms). In these figures, the indicated normal ellipses are a trifle larger than those based on short (ellipse B), and its ascending erect growth the Wang 700 output (the value of k changes fi-om about 7 to habit when competing with erect plants (points A) about 8). may equal or exceed the heights attained by al-

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46 ligatorweed and A, sessilis (ellipses C and F). The may contribute to A. hassleriana haying such short stem diameter shows less clearly the greater stem ascending stems when it is a more or less isolated, diameter of A. hasaleriana and the smaller diame- noncompeting, free-floating plant. In insolated ter of A. sessilis than is shown in figure 48. lagoons in South America, A. hassleriana occurs As observed by Chodat (1917), the floating stem either as isolated floating stems or as loosely woven of Alternanthera hassleriana is stabilized by a mass mats in which ascending stems are of the usual very of fine roots extending beneath the water surface. low profile. In contrast, the more or less free- They counterbalance the pair of erect leaves emerg- floating, noncompeting stems of alligatorweed as- ing above the water at each node, and a long ascend- cend with tapering, elongated stem intemodes and ing stem would interfere with this stability (ñg. 7). slender leaves. These usually emerge from the Such stability and such a rigidly consistent orienta- margins of incipient (in South America) or estab- tion of leaves and of root masses are not evident in lished (pre-biocontrol in the Southern United alligatorweed even when it is trailing on the ground. States) floating mats of the plant. Dense floating A floating growth habit that compares with that mats with emergent, erect, competing stems 300 to of Alternanthera hassleriana has yet to be found 1,000 millimeters tall, such as alligatorweed formed in alligatorweed. commonly in the Southern United States, were Somewhat comparable with A. hassleriana, never found involving either of these aquatic ama- however, may be the stems emerging from the ranths in South America. margins of incipient floating mats of alligatorweed Both plants have about the same ascending capa- that occur occasionally in South America or from the bility when competing with other stems. However, margins of the extensive, established floating mats as indicated above, Alternanthera hassleriana does that were commonplace in the Southern United not ascend when competing intraspecifically in open States (see frontispiece). Each of these more or less lagoons. Almost all erect A. hassleriana plants ob- isolated and noncompeting stems represents new served in South America were competing in dense growth; each emerges from the water surface in a growths of Eichhornia. For either amaranth, the broad gentle curve, ascending usually not more surrounding competing erect stems provide needed than 2(X) millimeters. A few such stems are included mechanical support. In addition, both in South in the sample represented in figure 47 by ellipse C. America and in the Southern United States, al- But a single example from a lagoon near Santa Fe, ligatorweed stems have been fqund to ascend to Argentina, having exceptionally large-diameter in- heights of 2,000 to 3,000 millimeters by climbing ternodes has been plotted separately on figure 47 from branch to branch of shrubs and bushes, which (point E) for comparison. The grossness of this plant provide the needed mechanical support for these approaches that of the floating form of A. has- weakly rigid, normally trailing plants. sleriana, which is not known to occur so far south in In figure 48, stem size is expressed by length and South America. width at the midpoint of the stem internode reach- The lagoons near Santa Fe are in the broad flood ing within 80 millimeters of the terminal meristem. plain of the Paraná River above its delta. They are Based upon the samples measured, which are rep- insolated and resemble the lagoons in the Chaco, resentative of the prevalent growth habit of each 500 kilometers upriver, where Alternanthera has- plant species, the internode diameter and to a less slerinnxL grows to the exclusion of alligatorweed, at extent the internode length of A. sessilis (ellipse F) least in undisturbed lagoons. In the 500 kilometers are smaller. They fall almost entirely within the separating Santa Fe and Resistencia, we do not range of variations of alligatorweed (ellipse C). In know just where A. hassleriana reaches the south- contrast, the prevalent decumbent, floating growth ernmost limit of its range. We believe it is likely that habit of A. hassleriana (ellipse B) has only a nar- this tropical plant does not reach appreciably row overlap with alligatorweed. It has a much beyond the confluence of the Paraguay River and larger range of internode diameter, but with inter- the Paraná River. It is very unlikely that alligator- node length falling within the range of alligatorweed develops a floating, lagoon-inhabiting growth weed. However, more nearly like the growth habit habit that really approaches A. hassleriana in form of alligatorweed, but in marked contrast with its or intergrades with it. own floating, decumbent growth habit, are the as- The film of water covering its hydrophilic floating cending stems of A. hassleriana that compete with stems and the weight of its more robust ascending erect plants such as occur within rafts of giant stems, together with their broad, heavy foliage, Eichhornia (points A). These stems remain distin-

47 Alt«rnanth«ra s«ssilis

A. philoxeroid«s

A. hassl«riana

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48 guishable from alligatorweed by their grossness, growth forms of each of the three species of aquatic their vestigially inflated internodes, and often by amaranths, are shown again in figure 49A. Here their appressed surface vestiture. they are shown in a suggested relationship with Included in figure 48 is a representation of stem their disonychine flea beetles, which are rep- size of the alligatorweed regenerating uniformly in resented by normal ellipses expressing the varia- an area where the stems had been covered with silt tion of the length to width of the pronotum for along the banks of the Reconquista River near females (fig. 49B) and males (fig. 49C). Buenos Aires (ellipse D). This alligatorweed had a The flea beetles of the genus Agasicles are history of heavy suppression by Agasicles hygro- grouped geographically to correspond with the phila. These stems are almost as slender as stems range and samples of the host plants (figs. 32-34). of Alternanthera sessilis (ellipse F), and virtually The Amazonian and Paraguayan forms of fasciate every one was infested at the time of sampling by at A. opaca are combined to correspond with the range least one clutch of ñrst-instar A^asici^s hygrophila of Alternanthera hassleriana, Agasicles vittata and larvae. Therefore, there was a high probability of its three other vittate congeners are combined in a attempted pupation within these stems at the same unit to correspond with the range of alligatorweed. time that there was a low probability of appreciable Inadequate sampling of the host plants prevented growth in stem diameter during the 2 weeks needed comparisons with individual species of Agasicles, for larval development. However, Agasicles vittata is shown separately be- The samples of alligatorweed were inadequate to cause, over part of its range, it is associated exclu- show significant differences in diameter among sively with Alternanthera sessilis (figs. 33 and 34). stems from the four regions where each of the four As explained earlier, this plant is also a host, but a vittate Agasicles species occur. This deficiency in minor one, for Agasicles vittata further downriver sampling required combining all these materials for and for A. interrogationis and A. connexa along the the comparative purposes treated in the next sec- narrow littoral of Brazil. In both of these regions, tion. For similar reasons, the Alternanthera has- alligatorweed is the major host plant. sleriana materials from the Paraguay and Amazon Because all these species of Agasicles pupate only Rivers were combined. inside their host-plant stem, each of the three sets Field observations indicate wide variation in of ellipses for Agasicles is connected by a line indi- stem diameters of alligatorweed for any given lo- cating interaction with the ellipse expressing varia- cality but with no recognizable change geographi- tion of host-plant internode length and width. No cally. Alternanthera hassleriana varies much less interaction is shown between the ellipse for at a given locality and shows no appreciable differ- Disonycha argentinensis and any of the host plants ence between the basins of the Amazon and Para- because, as indicated earlier, this flea beetle pu- guay Rivers. pates in soil. More than any other measurements made in this Flea beetles (recognized study, pronotal length and width show clearly the species) reduction of flea beetle width caused by restriction of the host-plant stem diameter. A slender pro- The means, standard deviations, and coefficients thorax, together with a somewhat narrowed head, of correlation of the 11 pairs of flea beetle charac- afford mobility within the stem internode cavity. ters measured on the 6 recognized disonychine This mobility is probably needed by the newly species are given in tables A-6 (females) and A-7 emerged flea beetle for feeding, either generally (males). Statistics are given in table A-8 and figure within the stem or in making an exit from the stem. 49 (B and C) for the combined samples of pronotal Also, we point out that the length and width of width (PrW) and length (PrL) for all four vittate pronotum in the pupa are nearly the same as in the species of Agasicles. adult (figs. 21-25). In contrast, this is not at all true Three of the bivariate normal ellipses in figure 48 of the elytra, to be discussed later. (B, C, and F), which represent the prevalent In comparing the ellipses of graphs B and C of

FIGURE 49.—Interactive evolution of amphibious amaranths and Agasicles species that pupate in the stem. The interaction is most* evident in the comparison of A, host-plant stem size (Int'n W and Int'n L), with B and C, pronotal size (PrW and PrL) for females and males of the infesting flea beetles. In Disonycha argentinensis, which pupates in soil, the pronotal width is much greater and the pronotal length much less than in the vittate species of Agasicles, (This figure is a coniposite of figs. 48 and 50.)

49 figure 49, representing the flea beetles, with those strikingly developed in Agasicles, Much less obvi- representing the host plants in graph A, it is evident ous sexual dimorphism is detectable from the that the stem diameters of Alternanthera sessilis graphs for three of the ten remaining sets and is tend to be undersized for the pupating flea beetles, summarized in table 5. while those of alligatorweed tend to be slightly Figure 50 represents the relationship of pronotal oversized; those of A. hassleriana are markedly width (PrW) to pronotal length (PrL). The ellipses oversized. From this it may be concluded that A. all show rather strong positive intercharacter cor- sessilis has the most restrictive stem diameter and relations, there being consistent alinement among A. tmssleriana the least (if at all) restrictive diame- them. Clear taxonomic discrimination is apparent in ter. Also, both A. sessilis and alligatorweed, the the normal ellipses representing Disonycha argen- normal hosts of the yittsite Agasicles species, have tinensis and Agasicles opaca. more restrictive stem diameters than does, if it does The phenocline between Disonycha argentinen- at all, Alternanthera hassleriana^ the normal host sis and Agasicles hygrophila shows a marked re- plant of the three fasciate forms of Agasicles. duction in width and a moderate increase in length. Alternanthera sessilis y however, does not occur Between A. hygrophila and A. opaca there is a within the range of the smallest vittate species, general increase in length and width, with the mean Agasicles hygrophila. points for the vittate species rather closely clus- The ellipses for the combined vittate species of tered. The considerably smaller size of A. hygro- Agasicles show that reduced insect width was ac- phila, the only species ranging into a temperate companied by a compensating increase in length. climate, is also evident in figures 51 and 52 with The fasciate forms, whose host plant has large stem respect to body (elytral) width, body length, and cavities, has increased in overall si^e considerably body thickness. The smaller size might seem to be beyond the dimensions of the vittate species of related to restrictive growth conditions besetting Agasicles and Disonycha argentinensis. This over- alligatorweed during summer, late fall, and winter. all size increase may have developed after various These temperate-climate conditions might seem to compensating length increases in the vittate ances- be most pronounced in their effects on alligator- tral form of the Paraguayan form of A. opaca, i.e., weed regenerating from attack by Agasicles, How- when it was a vittate species not far removed from ever, we have no consistent evidence that shows the earlier ancestral form resembling small-sized geographical differences in alligatorweed regenera- Agasicles hygrophila (fig. 40 between C and D). tion in South America. Nor do we have any evidence Figures 50 through 60 are the bivariate normal that Agasicles hygrophila is any more suppressive ellipses for 11 different sets of character pairs. Each of alligatorweed than any of its vittate allopatric set is composed of a series for the females (A) and a congeners. Also, as already pointed out, A. vittata, series for the males (B) of five forms of Agasicles ^ a species of intermediate size, is limited to and the related Disonycha argentinensis. In each Alternanthera sessilis over part of its range. This series, the heavy line connecting the mean points amphibious amaranth is the one with the most slen- for each species represents, as described earlier, der stemSy A: reineckii excepted. Therefore, the the first-version phenocline, or the estimated small size of Agasicles hygrophila remains an evolutionary trend. The sequence of the six species enigma unless it is a manifestation of relationship to is the same as that given for Recent time in the the similar-sized, closest extrageneric relative, dendrogram shown in figure 40. For the fasciate Disonycha argentinensis, If true, we can extend Agasicles opaca normal ellipses are given only for this explanation to account for the progressive in- the combined samples collected in the Paraguay creases in size from A. hygrophila to A. connexa to River and in the lower Amazon, 1960-61. Samples A. interrogationis and A. hygrophila to A. vittata collected in 1975 combined with the 1960-61 sam- (figs. 50-52). ples will be considered in the next section. On the other hand, the great size increase of Even though the configurations of the pheno- Agasicles opaca is more clearly attributable to the clines are diverse, in each of 10 of the 11 sets there large stem cavity of its host plant, Alternanthera is remarkable concordance between trends for the hassleriana (figs. 50-52). In contrast with the vit- females (A) and the males (B), indicating little to no tate species that are clearly limited in size by stem sexual dimorphism. In a single set (fig. 60), how- diameters of A. sessilis and by alligatorweed, the ever, there is marked discordance, clearly repre- forms of Agasicles opaca consistently have space to senting the obvious sexual dimorphism that is so spare for pupation in the internode of Alter-

50 nanthera hassleriana (fíg. 49). However, when only limited reduction and is considered to be a the fasciate forms pupate in alligator weed, stem- less sensitive measure of constrictive effects size limitation must come into play to limit flea of the host-plant stem than is the pronotum. beetle size. It may be significant that our experi- Figure 52 represents the relationship of body ence with the Amazonian Agasicles opaca shows length (TBL) to body thickness (BTh). Again con- much less association with alligatorweed (almost sistently alined, the ellipses show strong inter- none) than does the Paraguay River form. This character correlation. Except for the combined difference may relate to the smaller size of the Agasicles opaca forms, they show no clear tax- Paraguayan form as compared with Amazonian onomic discrimination among the species. fasciate forms and reflect restrictive stem size be- The phenocline approaches a straight line with ing imposed by alligatorweed. The size of the little separation between Disonycha argentinensis Paraguayan and Amazonian forms of A. opaca will and Agasicles hygrophila. The slope of the pheno- be taken up in the next section. cline represents a gradual size increase. As indi- Figure 51 represents the relationship of elytral cated in the previous discussion, width as well as length (EL) to elytral, or body, width (EW). Being length has control over body thickness. Accord- consistently alined, the ellipses show strong inter- ingly, as flea beetle size increases, length of body character correlations, which are positive in all increases more than thickness of body, with the cases. There is more range of variation longitudi- greatest increases being attained by Agasicles nally than transversely to the body axis. Except for opaca. This progressive differential rate of increase the combined fsiscisite Agasicles forms, the normal is also more or less evident in figures 51 and 55-60 ellipses show no clear taxonomic discrimination be- and indicates clearly a consistent tendency in tween the species oí Agasicles. Agasicles to increase in size. The progression From soil-pupating Disonycha argentinensis, corresponds with increasingly tropical climates on the phenocline shows a significant although small one hand and increasing distance from the range decrease in elytral width, with little change in of Agasicles hygrophila on the other. It may also length, a reduction presumably permitting better correspond with an increase in host-plant stem di- fit of Agasicles hygrophila inside the host-plant ameter in some way not presently recognized. stem. As flea beetle size increases, elytral length Both figures 51 and 52 show a discontinuity in the increases more than width, with the greatest in- trend between A. interrogationis and A. vittata. crease in width and length being attained by the This will reappear in figures 55, 56, and 58. combined A, opaca forms of Alternanthera has- Figure 53 represents the relationship of head sleriana. Note the extent of the steep slope of the width (HW) to head length (HL). The ellipses are trend between the large fasciate species and the variously oriented, with the two for the female smaller vittate species. Agasicles connexa and A. interrogationis hav- Across the elytra (elytral width) is the widest ing negative coefficients of correlation. But even portion of the adult body. But the elytra are so, no clear taxonomic discrimination is evident wrapped around the body of the pupa and are ac- among species. tually exceeded laterally by the apices of the pro- The mean points of the ellipses are rather closely jecting rigid femora (figs. 22 and 23). The elytra clustered; and although the head width of adult and are among the last body parts to be extended and pupa are less than the pronotal width (figs. 1-6 and sclerotized during and after ecdysis. They remain 21-23), head width is significantly reduced in the in a pliable condition while the newly emerged, un- phenocline from Disonycha argentinensis to Aga- fed, and still not full-sized adult remains inside the sicles hygrophila. As body size increases, head size stem. In the adult the elytra enclose the ptero- fluctuates in a narrow range from A. hygro- thorax and abdomen that in turn house the large phila through the vittate species and then mark- flight muscles and the space-demanding ovaries. edly to the combined forms of A. opaca. Head The ratio of width to thickness to length of body length shows less change than width over most of can only undergo limited adjustment without seri- the phenocline. ously interfering with the flea beetles' jumping Figure 54 represents the relationship of interocu- ability to avoid danger. Already, slenderization lar width (lOW) to interantennal width (lAW). The of body and appendages seems to have rendered ellipses are rather consistently alined, with all coef- Agasicles less agile than its disonychine relatives. ficients of correlation positive. Except for the com- Therefore, elytral width probably can undergo (Continued on page 7Jf. )

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73 bined fasciate forms, the normal ellipses show no Figure 56 represents the relationship of antennal clear taxonomic discrimination among the species length (AL) to metathoracic tibial length (MTL). of Agasicles. The normal ellipses are all consistently alined and The configuration of the evolutionary trend line have positive coefficients of correlation, with the is remarkable. It shows a very large decrease in exception of the female Disonycha argentinensis both variâtes from Disonycha argentinensis ellipse, which is rotated more than 90° counter- to Agasicles hygrophila and a further marked de- clockwise to a negative coefficient of correlation, crease in the I AW continuing to A. connexa. Then in contrast with the ellipse for the male. No there follows an increase in lAW with a decrease in clear taxonomic discrimination is evident among low continuing to A. interrogationis, Both vari- these ellipses. âtes increase moderately, continuing to A. vittata, For the first time, the mean point of a vittate followed by the greatest increase in both variâtes Agasicles, A. vittata, falls closer to A. opaca along continuing to the combined fasciate forms. the phenocline than do two other vittate species, in The striking irregularities in this pair of pheno- this case, A. interrogationis and A. connexa. As clines demonstrate the latitude of diversity of shown in table 5, this proximity reappears in the widths that can occur in the flea beetles indepen- phenoclines for antennal segments (figs. 57, 58, and dently of host-plant stem diameters and indepen- 60). In all these cases, the greater proximity is dently of a general trend of increasing flea beetle limited to the females and is evidence of sexual body size (compare with figs. 50 and 52). None of dimorphism (which is less obvious in figs. 56-58 but these widths abut against the interior of the stem very obvious in fig. 60). cavity or earthern pupal cell. These widths un- The phenocline between Agasicles hygrophila dergo as much change among the closely related and fasciate A. opaca is nearly straight, with both species as among the less related. Despite the ir- variâtes increasing in value and their mean points regular phenocline for this character, its useful- being rather evenly distributed along its length. A ness for taxonomic purposes is not borne out by decrease in length occurs in both the antenna and the consistent alinement of the normal ellipses. the tibia between Disonycha argentinensis and Figure 55 represents the relationship of max- A. hygrophila. Also, these and the next two sets imum width of the base of the black U-shaped elytral of measured antennal characters are pairs of marking (U2W, fig. 46) to minimum width of the lengths and cannot show the slenderization that base of the ivory U-shaped elytral marking (UIW, has taken place in the antennae and legs (femora) fig. 46). The normal ellipses for each of the species of Agasicles as compared with Disonycha argen- show various orientations, with all coefficients of tinensis (figs. 1-6). correlation negative except for female Agasicles Figure 57 represents the relationship of the connexa and male Disonycha argentinensis. The lengths of the fourth antennal segment (4AL) and ellipses for the combined fasciate forms are com- the third antennal segment (3AL). The normal pletely discrete, and those for A. hygrophila over- ellipses are consistently alined and have positive lap only slightly those for A. connexa and A. vittata. coefficients of correlation, with the exception of This character is diagnostic for the identification of the female Disonycha argentinensis and female the combined fasciate forms and for A. hygrophila. Agasicles connexa ellipses. The ellipse for females The phenocline is remarkable for the out-of-line of A. connexa is inordinately large because of the or switchback position of the mean point for small size of the measured sample and its great Agasicles vittata. This discontinuity is also evident variation. The normal ellipses show no clear taxon figures 51, 52,56, and 58 and may point to a more onomic discrimination among species along the remote relationship with A. interrogationis. The phenocline. increase in U2W is probably related to body elonga- The phenocline shows the two antennal segments tion in the process of size increase in Agasicles gradually and rather evenly increasing in length species; and in this connection, the mean values for from Agasicles hygrophila through the combined the character proportion are nearly equal for A. fasciate forms, with a marked, seemingly spurious hygrophila and its closest extrageneric relative, deviation by the female of A. connexa. From Disonycha argentinensis. There is the usual con- Disonycha argentinensis to A. hygrophila there is a cordance in the trend lines for the females and significant reduction in length of 3AL but only a males, indicating that there is little or no sexual slight reduction in 4AL. dimorphism shown by this pair of characters. Figure 58 represents the relationship of the

74 lengths of the sixth antennal segment (6AL) and width (PyW) and pygidial length (PyL). The normal the fifth antennal segment (5AL). All the normal ellipses for the females show little alinement, with ellipses have positive coefficients of correlation. In the ones for Agasicles connexa and A. inter- the females there is no elliptic angle exceeding 45°, rogationis having negative coefficients of correla- while in the males the alinement is more nearly tion and affording taxonomic discrimination. In perfect, with elliptic angles not exceeding more considerable contrast, the ellipses for the males than a few degrees. All of the ellipses broadly over- are somewhat consistently alined with the ones lap one another and show no clear taxonomic dis- for A. interrogationis and combined A. opaca crimination among species along the phenoclines. forms and have only slightly negative coeffi- Along the phenocline this set of relationships cients of correlation. shows the greatest proximity between the vittate A much greater contrast exists between the Agasicles species and A, opaca. The phenoclines phenoclines for the females and the males. As are almost straight, with about a 1 : 1 slope, indi- pointed out earlier, this is a manifestation of obvious cating that antennal segments have increased in sexual dimorphism and reflects the development of size rather regularly in the evolutionary course. the keellike horns on the female's pygidium, the As it does in the phenoclines for other plottings, "ke/' of the external genitalia characteristic of the Agasicles vittata deviates slightly from the usual genus Agasicles, This key is vestigial in the males. trend. Disonycha argentinensis makes a similar But developed on the venter of the male abdomen is deviation from the general course of this trend. the remarkable cavity, or "lock," which receives the Figure 59 represents the relationship of the key of the external genitalia. Because of lack of length of the seventh antennal segment (7AL) and suitable corresponding reference points in most its width (7AW). The normal ellipses for the females females, no measurements were made of the lock in show very little alinement, and the axes for this study. Agasicles connexa and A. vittata have negative In the females, between Disonycha argentinen- coefficients of correlation. In considerable contrast, sis and Agasicles connexa^ the phenocline shows the ellipses for the males are somewhat consistently that the increase in width of the pygidium is accom- alined, and only the one for A. connexa has a alight panied by little change in length. But continuing to negative coefficient of correlation. There is much A. interrogationis y there is a striking increase in overlapping and some near superposition of the length, with little increase in width. A significant ellipses except for that of combined A. opaca reduction in length with a small increase in width forms, which is nearly discrete for the females ensues to A. vittata. A large increase in width, with and completely so for the males. In the next sec- a small decrease in length, follows to the combined tion, we will see from the second-version pheno- A. opaca forms. In comparison, in the males, be- clines that this discreteness of combined Agasicles tween A. hygrophila and the combined A. opaca opaca forms is lost to a considerable degree when forms, the width increases with the overall body the samples are subdivided geographically. size, but the length diminishes somewhat before The phenocline takes a rather uneven course, but gradually increasing between A. interrogationis there is clear concordance between the trends for and the combined fasciate forms. The sexually di- females and males. Between Disonycha argen- morphic external genitalia seemingly evolved de tinensis and Agasicles hygrophila there is a slight novo and may have been instrumental in the specia- reduction in the width of the antenna, and between tion of Agasicles. D. argentinensis and A. vittata there is a slight Table 5 summarizes the proximity between the average decrease in the width as the length gradu- vittate Agasicles and the combined fasciate A. ally increases. This trend may also be a mani- opaca forms, based on phenoclinal distances for festation of the slenderization of appendages that each of the 11 character pairs. As already noted, facilitate fitting the vittate species of Agasicles greater proximity does occur between vittate A. within the confines of the stem cavity. The steep vittata and fasciate A. opaca than between vittate slope of the phenocline between A. vittata and the A. interrogationis and vittate A. connexa. This combined fasciate A. opaca forms may reflect a greater proximity is.limited to females for the obvi- reversal in trend afforded by the lack of restric- ous sexually dimorphic character pair PyW to PyL, tion inside the large stem cavity of Altemanthera and for the three less obvious sexually dimorphic hassleriana. character pairs that involve antennal length, Figure 60 represents the relationship of pygidial namely, AL to MTL, 4AL to 3AL, and 6AL to 5AL.

75 Table 5.—First-version phenocline distances between mean points of character pairs of Agasicles species as shown in figures 50-60. Decreasing values of differences indicate increasing proximity between the yitt^te Agasicles species and A. opaca. Negative values indicate that the distance between vittateA. vittata and fasciateA. opaca is less than the distance between vittateA. interrogationis and vittateA. connexa [Millimeters]

Character Females Males (It^oy) A.vittata A. connexa to r»iff*.ran.o A. vittata A, connexa to ^ ^^ toA. opaca A. interrogationü ^^^^^^^^ to A. opaca A. interrogationis ^'^^^^^""^^ PrWtoPrL(fig.50) 152 13 +139 152 6 7l46 EL to EW (fig. 51) 90 27 +63 84 38 Í7(^ BLtoBTh(fig.52) 75 30 IZ fo 20 ^50 HWtoHL(fig.53) 62 15 +47 61 6 +55 IOWtoIAW(fig.54) 107 29 +78 112 22 +90 U2WtoUlW(fig.55) 125 34 +91 117 26 tfl AL to MTL (fig. 56) 26 38 -12 58 34 +24 4ALto3AL(fig.57) 34 43 -9 61 34 +27 6ALto5AL(fig.58) 45 70 -25 64 52 +12 7ALto7AW(fig.59) 97 22 +75 106 19 +87 PyWto PyL (fig. 60) _70 91 -21 68 28 +4^^ '^^^^ ^ 412 +538 953 285 +668 -67 _0

The straight-line distances between the mean distances (not indicated in table 6) correspond to points of character pairs îor Disonycha argentinen- those of the males. sis (base zero) and those for each Agasicles species are given in table 6. The progression from D. argen- Flea beetles (subspecifíc tinensis to A. opaca for each of the mean points forms oi Agasicles opaca) varies from the more even ( $ U2W to UIW and The quantitative studies reported in the previous çf PyW to PyL) to the more uneven ( $ lOW to lAW section relate to flea beetle species or populations ande/low to I AW). The totals for each of the flea that we consider as being reproductively isolated. beetle species constitute a rather even progression Figures 1-6 show differences in the external lock- for both females and males, with Agasicles vittata and-key genitalia of these forms, while figures showing a tendency to deviate. For those pheno- 26-31 show less obvious differences in the uncleared clines that are irregular, the serial order pre- aedeagi. Additional study material acquired in sented in the dendrogram (fig. 40) and in the charts South America in 1975 enables us to reconsider the results in greatest consistency. Different ordering subspecifíc forms oí Agasicles opaca in more detail. of the series results in greater overall inconsis- Previously, when our material was limited to the tency. For these reasons, and in consideration of two extreme ends of their range, we considered that the background information previously given, the fasciate A^asici^s might be composed simply of we believe the relative proximity of the mean two species. This judgment was based on markings points for the Agasicles species and Disonycha ar- and on a rather wide separation between most of the gentinensis expresses relationship. mean points of the two forms along the phenocline in We also note from table 6 that for only a sin- which the lower Amazonian form is consistently gle character pair, lOW to lAW, does a female most distantly removed from Disonycha argen- vit täte Agasicles exceed A. opaca in the distance tinensis (in table 6, we show only the straight-line separating it from Disonycha argentinensis. In distance for the combined Paraguayan and Amazo- the males, A. opaca is not exceeded on a straight nian forms oí Agasicles opaca). Furthermore, we line in any of the 11 character pairs. Additionally, anticipated that the two forms would separate as 7 of the 11 female maximum distances correspond Paraguayan and Amazonian. However, additional to those of the males, while 9 of the 11 minimum samples have tended to obscure the separation

76 Table 6.—Straight-line distances between mean points (figs. 50-60) of body proportions of Disonycha argentinensis sind Agasicles species. Maximums within vittate Agosic/es species are in brackets. Max- imums that are concordant between females and males are starred [Percent of total]

Character D. pair A. A. A. A. A. argentinensis (xtoy) hygrophila connexa interrogationis vittata opaca

FEMALES

PrWtoPrL(fig. 50) .... 0 [19.5]* 17.6 17.6 16.2 29.2 EL to EW (fig. 51) 0 7.0 5.1 [17.8]* 15.4 54.7 BLtoBTh(fig. 52) 0 0.9 9.0 [21.4] 18.3 50.4 HWtoHL(fig.53) 0 [22.4]* 8.0 20.0 16.0 33.6 low to lAW (fig. 54) .... 0 18.7 [24.6]* 23.4 18.7 14.6 U2WtoUlW(fig.55) ... 0 0.6 17.6 [24.8]* 17.6 39.4 AL to MTL (fig. 56) 0 6.0 6.0 22.1 [26.8]* 37.9 4ALto3AL(fíg. 57) .... 0 13.6 7.8 20.5 [23.0]* 35.0 6AL to 5AL (flg. 58) .... 0 6.0 10.3 [26.8] 23.1 33.9 7ALto7AW(fig.59) .... 0 6.5 13.6 [18.8] 17.2 43.9 PyWtoPyL(fig. 60) .... 0 3.0 10.1 [26.8] 23.3 37.0

Total 0 9.0 13.0 22.3 19.6 36.2

MALES

PrWtoPrL(fig. 50) .... 0 [19.7]* 15.3 16.4 16.2 32.4 EL to EW (fig. 51) 0 5.6 2.3 [18.5]* 18.1 55.6 BLtoBTh(fig. 52) 0 2.8 2.5 15.9 [16.5] 61.1 HWtoHL(fig.53) 0 [19.4]* 5.1 11.2 11.2 53.1 low to lAW (fig. 54) .... 0 16.1 [22.6]* 21.6 15.8 24.0 U2WtoUlW(fig.55) ... 0 2.8 17.5 [23.2]* 17.3 39.1 AL to MTL (fig. 56) 0 6.5 6.9 17.8 [23.1]* 45.8 4ALto3AL(fig. 57) .... 0 12.9 10.4 15.4 [20.4]* 41.0 6ALto5AL(fig.58) .... 0 3.1 9.6 23.1 [23.8] 40.4 7ALto7AW(fig.59) .... 0 4.9 12.9 14.7 [20.0] 47.6 PyWtoPyL(fig. 60) .... 0 5.4 7.1 14.3 [26.8] 46.5

Total 0 8.7 11.5 18.1 19.3 41.9 along the phenocline and have revealed no clear landscapes constitutes a major center of Alter- evidence of reproductive isolation. Besides, instead nanthera hassleriana and Agasicles opaca. Within of a Paraguayan and an Amazonian form, we now 600 kilometers of the Plains of Mojos are the la- consider three subspecific forms as more likely. goons and associated wetlands of the Paraguay Accordingly, we assigned the samples of A^a- River basin, the third major center of Agasicles sicles opaca to three very large geographic re- opaca and its host plant. This vast region includes gions among which, we postulate, there is now only the Pantanal and much of the Gran Chaco. The restricted gene flow. The first of these regions is the interface of the Madeira River (Amazon) basin and broad deltaic plain of the lower Amazon River. the Paraguay River basin crosses the Santa Cruz Much of this is open landscape studded with iso- Department of Bolivia and the Planalto do Mato lated insolated lagoons that are natural habitats Grosso. The first is a region of mostly low but sea- of Alternanthera hasslerianay the normal host of sonally dry relief, and the second is a region of Agasicles opaca. A broad region of forest and a long narrow valleys. Both seem to lack conditions stretch of rapids of the Madeira River together with needed for lagoon formation. Under present condi- a narrow alluvial plain and a paucity of lagoons tions, a trickle of gene flow could exist between the separate the lower Amazon from the second region, Candelaria River (Paraguay Basin) and the upper the Plains (Llanos) of Mojos. Within the Amazon reaches of the Guaporé River (Amazon Basin). Basin, this vast region of seasonal flooding and open The ecological homology existing among the

77 species oí AgasicleSy together with their biogeog- more generally and evenly over the aquatic portions raphy and the dispersal capability demonstrated in of its habitat than does alligatorweed. The reverse the United States hy Agasicles hygrophilay indicate is true, however, for their occurrences over the that gene flow may be important as a cohesive force terrestrial portions of their habitat ranges (Vogt et in the speciation within this genus (Mayr 1970). al., cited in footnote 8). To match this information However, Ehrlich and Raven (1969) and Ehrlich et indicating greater homeostasis in the interaction of al. (1975) consider that "gene flow in nature is much host plant and fasciate Agasicles species as com- more restricted than is commonly thought and ex- pared with the interaction of host plant and vittate perimental evidence is badly needed to document Agasicles species, we have no information on the the extent to which it does occur." They believe that dispersal capability of the fasciate Agasicles forms natural selection operating upon localized small to compare with what we have on A. hygrophila in populations is the more important evolutionary the United States (Vogt et al., cited in footnote 20). mechanism. They consider further that climatic dif- With these considerations in mind, we proceed ference constitutes an important selective feature: with an analysis of the second-version phenoclines "Our data support the generalization that differen- and the normal ellipses for the fasciate Agasicles tiation will occur in the presence of gene flow or will forms. not occur in its absence depending on the regime." The most variable character within Agasicles The results we present next in this and in the opaca is the elytral markings. In figure 61, 10 following section will show that divergence among graded variants of elytral markings represent the the three geographic forms of Agasicles opaca is range of variation in 137 specimens of A. opaca from less than has occurred among the four vittate the 3 regions just described. Since we will consider Agasicles species. However, the divergences be- quantitatively only one set of character proportions tween the vittate group of species and the fasciate based on markings, namely U2W to UIW, we pre- group of forms are mostly even more extensive. We sent in table 7 the frequency distribution for the 10 interpret these findings to mean that having un- illustrated variants. It is evident that the lower dergone most of its evolution interacting with Amazon River form and the Paraguay River form small-stemmed alligatorweed, fasciate polytypic rather clearly constitute two rather even, distinct Agasicles opaca diverged from the vittate forms, patterns, while the distribution of the Plains continuing its evolution interacting mostly with the (Llanos) of Mojos form tends to make a rather un- oversized stems of Alternanthera hassleriana. even overlapping third distribution pattern. While this release from interaction with small stems We now consider the three geographic forms of relates to an accelerated rate of divergence from Agasicles opaca quantitatively with respect to the the vittate forms, it also relates to slowed evolu- same 11 pairs of character pairs studied in the pre- tion of reproductive isolation and therefore specia- vious section. Figures 62 through 72 show the tion among the fasciate forms. Furthermore, the bivariate normal ellipses for the 11 different charac- larger-sized fasciate Agasicles forms may have ter proportions. As before, each set is composed of a greater vagility than the vittate species, which series for the females (A) and a series for the males remain under the constraints of restrictive under- (B). In each series the heavy line connecting the sized host-plant stems. Greater vagility should re- mean points for each subspecific form is the pheno- sult in greater gene flow over geographic barriers, cline. It is continuous with the phenocline of the which we judge to be comparable in resistance vittate species, which is shown without normal el- against either the vittate or the fasciate Agasicles lipses. A dotted line connects the phenoclines of the forms. We conclude that the slowed speciation rate vittate species and the fasciate forms, and, at the among the fasciate Agasicles forms may be a result other end, the mean point for Disonycha argen- of greater gene flow. tinensis. The total phenocline constitutes the sec- However, there seems to be little in our field ond version oí the Disonycha-Agasicles phenocline. results to support this conclusion. Probably because Again the sequence of the four vittate species and of the floating nature and other attributes of its host the three fasciate subspecific forms is the same as plant, Alternanthera hassleriana (fig. 7), the fas- that given for Recent time in the dendrogram ciate A^asic/es forms (and Vogtia malloi) are not as shown in figure 40. The scales of the second-version extirpative in their depredations as are the vittate phenoclines are adjusted to be subequal to those of Agasicles species (and Vogtia malloi) on alligator- the first version. weed. As R result Alternanthera hassleriana occurs Generally, for most character proportions, the

78 2 mm

FIGURE 61.—Ten graded variants of elytral markings, A to J, selected from the 137 specimens (70 females and 67 males) of Agaskles opaca studied quantitatively (described in table A-9). Variant J is intermediate between variants I and A. Similarly each of the other variants is intermediate between the preceding and succeeding variant. phenoclines of the fasciate forms of Agasicles are crease (+) of difference" in table 8. In a few charac- shorter than those for the vittate species and un- ter pairs, the reduction is marked. This increased dergo somewhat comparable changes. Usually, the proximity results from organizing the samples of concordance between the female and male pheno- Agasicles opaca into three geographical forms, of clines more or less continues. As compared with the which individuals of the Paraguay River form are first-version phenoclines presented in the previous significantly smaller in size than those of the lower section, we find less separation between the mean Amazon River form. While the proximity between points of the proximate forms of vittate and fas- vittate Agasicles vittata and the Paraguay River ciate Agasicles for most character pairs. This form of fasciate A. opaca increases along the change is tabulated under "reduction (-) or in- phenocline, there is no increase in the number of

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80 character pairs having vittate Agasicles mean ing slightly within. There is no calibration correc- points nearer those of the fasciate forms than those tion to affect either of these sets of character pairs. of other vittate species. The phenoclines for both sexes show a switch- In part, because of this increased proximity along back that seems to be comparable to those occur- the phenocline, there is greater overlapping of ring between vittate Agasicles interrogationis and the ellipses of the fasciate and vittate Agasicles A. vittata. Again, as size increases, length in- species. Also, in part, because there is too little creases more than width. However, the general separation along the phenocline, there is no signifi- slope of the phenocline changes little in passing cant taxonomic discrimination among the normal el- from the vittate species through the fasciate forms. lipses of the three forms of fasciate A^rasicies opaca. Figure 64 represents the relationship of body For most character pairs, the normal ellipses of the length (TBL) to body thickness (BTh). Still again, fasciate forms have comparable form and are ori- the ellipses show the same strongly positive inter- ented similarly to those of the vittate species. character correlation as do those for the vittate flea Generally, for each character pair, one of the three beetles (fig. 52). There is wide overlapping and no separate normal ellipses of A. opaca or more taxonomic discrimination among the three fasciate extends beyond the corresponding normal ellipses forms. The ellipses for the females extend slightly for the 1960-61 combined samples presented in the beyond that based on the 1960-61 combined sam- previous section (figs. 50-60). Three causes for ples. Again, there is nearly perfect coincidence of these differences are: (1) reduction of sample size the ellipses of both sets for the males. As in the through division into three geographic forms; (2) previous character proportion, the slope of the increase of variance as a result of additions to sam- phenocline shows no persistent change, and again ples from the collections in 1975; and (3) inadequate there is a short switchback that is comparable to adjustment of the x and y scales to compensate for that occurring between vittate Agasicles inter- calibration errors (see p. 43) applied exclusively in rogationis and A. vittata. the previous section to the 1960-61 samples. This and the two preceding character pairs, the Figure 62 represents the relationship of prono tal phenoclines of the fasciates, show the late stages of width (PrW) to pronotal length (PrL). The ellipses the dramatic size increase that occurred since the show the same strong positive intercharacter corre- vittate ancestral form near Agasicles hygrophila lation as do those of the vittate species shown on first became associated with the floating inflated- figure 50. In both sexes the phenocline changes stem Alternanthera hassleriana. It is clear from slope to show an extended strong tendency for the phenoclines that the lower Amazon form is a elongation of the prothorax with little increase in larger insect than is the Paraguay River form, while width. This change is inconsistent with the concept the Plains of Mojos form is only slightly larger. that release from interaction with a constrictive Figure 65 represents the relationship of head stem should result in more broadening than elonga- width (HW) to head length (HL). These ellipses are tion. Possibly, the effects of the release have run closely clustered and are broad to almost circular in their course, and another adaptive course has set in. form. In these respects, they are similar to those for Although the phenocline is moderately long (longer the vittate flea beetles (fig. 53). The latter ellipses than that of the vittates in the males), the ellipses are more variously oriented, however. The ellipses overlap very broadly, there being no significant for both sexes of the three forms of Agasicles opaca taxonomic discrimination. The ellipses of the indi- extend widely beyond those based on the 1960-61 vidual geographic forms extend beyond those based combined samples (fig. 53). The scales of the on the combined 1960-61 samples (fig. 50). In the second-version phenoclines are about subequal to females, the extension is broad, while in the males, those of the first version. The fasciate Agasicles it is narrow. species show some of the general directional change Figure 63 represents the relationship of elytral that characterizes the vittates. length (EL) to elytral, or body, width (EW). Again Figure 66 represents the relationship of interocu- the normal ellipses show the same strongly positive lar width (lOW) to interantennal width (lAW). The intercharacter correlation as do the vittate flea normal ellipses tend to show the same positive in- beetles (fig. 51). There is no taxonomic discrimi- tercharacter orientation as those for the vittate flea nation. The ellipses for the females extend beyond beetles (fig. 54). Although the phenocline is moder- those based on the 1960-61 combined samples. ately long for the fasciate forms, the ellipses are too Those for the males coincide almost perfectly, fall- (Continued on page 87. )

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FIGURE 63.—Means and bivariate normal ellipses (second version) for relations in flea beetles between elytral length and width. A, Females. B, Males. The solid line connecting the mean points for each subspecific form is the phenocline of the fasciate forms. It is continuous with the phenocline of the vittate species, which is shown without normal ellipses. A dashed line connects these two phenoclines and, at one end, the mean point oiDisonycha argentinensis to form the second-version phenocline.

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FIGURE 64.—Means and bivariate normal ellipses (second version) for relations in flea beetles between total body length and thickness. A, Females. B, Males. The solid line connecting the mean points for each subspecific form is the phenocline of the fasdate forms. It is continuous with the phenocline of the vittate species, which is shown without normal ellipses. A dashed line connects these two phenoclines and, at one end, the mean point of Disonycha argentinensis to form the second-version phenocline.

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65 B

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FIGURE 65.—Means and bivariate normal ellipses (second version) for relations in flea beetles between head width and length. A, Females. B, Males. The solid line connecting the mean points for each subspedfic form is the phenocline of the fasciate forms. It is continuous with the phenocline of the vittate species, which is shown without normal ellipses. A dashed line connects these two phenoclines and, at one end, the mean point oíDisonycha argentinensis to form the second-version phenocline.

86 large and too closely clustered to allow taxonomic lengths just described is a manifestation of less ob- discrimination. Although the second-version vious sexual dimorphism and recurs in the length phenoclines are subequal to slightly smaller than of antennal character pairs presented in figures 69 those of the first, the ellipses for both sexes extend (4AL to 3AL) and 70 (6AL to 5AL). As indicated widely beyond those based on the 1960-61 combined by negative differences in table 8, both female and samples (fig. 54). male phenoclines show greater proximity between Figure 67 represents the relationship of max- the fasciate and vittate Agasicles species. In the imum width of the base of the black U-shaped elytral phenoclines based on the combined forms of fasciate marking (U2W, fig. 46) to minimum width of the A. opaca, the greater proximity is limited to the base of the ivory-colored U-shaped elytral marking females (table 5). (UIW, fig. 46). As with the vittate species of Figure 69 represents the relationship of the Agasicles (fig. 55), the ellipses for the fasciate forms lengths of the fourth antennal segment (4AL) and of A. opaca show various orientations that are nega- the third antennal segment (3AL). The normal el- tive for females of the Plains (Llanos) of Mojos form lipses tend to be consistent in form and alinement and for males of the Paraguay River and lower with those representing the vittate species (fig. 57). Amazon River forms. But the size and breadth of There is near superposition for the females and the ellipses and the moderate phenoclinal distances broad overlapping for the males. Having some out- prevent taxonomic discrimination among the fas- of-line orientation and a broader phenoclinal sep- ciate A^raszc/es for this character pair. The ellipses aration, the male ellipses show some tendency for for both sexes correspond well in general form to taxonomic discrimination. Both female and male el- the pair based on the 1960-61 combined samples. lipses extend broadly beyond the pair based on the But for both sexes, the ellipses of the subdivided 1960-61 combined samples (fig. 57). The phenocline samples extend moderately beyond those based on is irregularly longer in the females and subequal in the combined samples. The scale for the second- the males as compared with those of figure 57 in the version phenoclines is inadequately adjusted, being previous section. somewhat oversized. Figure 70 represents the relationship of the We note that the rather long phenocline of the lengths of the sixth antennal segment (6AL) and the fasciate Agasicles shows the same kind of discon- fifth antennal segment (5AL). The ellipses show tinuity, represented by a switchback, that occurs about the same strong intercharacter correlation as between A. connexa and A. vittata of the vittate do the vittate flea beetles shown in figure 58. Al- species. This feature is very apparent in the females though the phenoclines of the fasciate species are between the Paraguay River and lower Amazon moderately long, especially in the males, the el- River forms of the fasciate Agasicles. This type of lipses overlap very broadly and show no taxonomic occurrence on the same phenocline between geo- discrimination except that longer antennal seg- graphically contiguous forms raises some question ments characterize the Amazon River form in less about the validity of relating such a discontinuity to than half of the individuals in the females and more a major biogeographical isolation, as we have indi- than half in the males. The ellipses for both sexes cated in the case of A. interrogationis and A. vittata of the three forms of Agasicles opaca extend only (p. 74). In the same relative positions, this type of slightly beyond those based on the 1960-61 com- discontinuity recurs in both fasciates and vittates in bined samples (fig. 58). The phenoclines are slightly two previous sets of phenoclines (EL to EW and longer in both sexes as compared with those of TBLtoBTh). figure 58 of the previous section. Figure 68 represents the relationship of antennal Figure 71 represents the relationship of length of length (AL) to metathoracic tibial length (MTL). the seventh antennal segment (7AL) and its width The ellipses show the same strong positive inter- (7AW). For females, the normal ellipses are alined character correlation as do the vittate flea beetles quite closely. This is in contrast with the various (fig. 56). The ellipses are almost superimposed in elliptic orientations of the female vittate species the females, for which the phenocline is very short. (fig. 59A). For the males the three ellipses are vari- They overlap broadly in the males, for which the ously oriented, in contrast with the more consis- phenocline is quite long. The ellipses for both sexes tently alined male vittate species (fig. 59B). The extend very little beyond the pair based on the phenoclines are rather long, and the ellipses are 1960-61 combined samples (fig. 56). broadly overlapped to nearly superimposed. Al- The contrast between female and male phenocline (Continued on page 100.)

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99 though the phenoclines are somewhat longer, espe- the distance along the Agasicles phenocline for two cially for the females, all three ellipses for both character pairs in the females and seven in the sexes fall narrowly within the pair based on the males. For the females, the percentages range 1960-61 combined samples (fig. 59). from 43 to 79 and for the males from 38 to 71. Later Figure 72 represents the relationship of pygidial (p. 104), we will find that the order of the mean width (PyW) and pygidial length (PyL). As with the points of the third-version phenoclines results in the vittate species represented in figure 60A, the nor- vittates exceeding the fasciates for all character mal ellipses for females of the three fasciate forms pairs but three. These are judgmental comparisons, show various angles of orientation and the Plains not statistical statements, because of the small (Llanos) of Mojos form has a negative coefficient of sample size. correlation. Also, as with the vittate species, the Table 10 gives the successive phenoclinal dis- phenocline shows sharply changing trends. On the tances between mean points of the character pairs other hand, the males show the marked sexual di- (intermean point distances) for the vittate and fas- morphism that occurs in the vittate species. It is ciate Agasicles and Disonycha argentinensis as manifest in a continuation of the rather straight shown in figures 62-72. The totals of the intermean phenocline, which shows little vertical displace- point distances between the most derived vittate, ment, that is, change in pygidial length. The A. vittata, and the least derived fasciate Paraguay phenoclines for both sexes are moderately long, but River form of A. opaca are 723 (31 percent) for the the breadth and large size of the ellipses preclude females and 702 (31 percent) for the males. These appreciable taxonomic discrimination. Although exceed by far all other totals given in table 10 and the phenoclines have been scaled down to the point represent the widest evolutionary divergence along of being somewhat smaller than those of the previ- the phenocline. However, the distances are not ous section, all three normal ellipses extend appre- maximal for 4 of the 11 character pairs, namely, AL ciably (more so in the males) beyond those based on to MTL, 4AL to 3AL, 6AL to 5AL, and PyW to the combined samples oîAgasicles opaca (fig. 60). PyL. Each of these is surpassed by one to four of the We attribute the larger size of these ellipses to the other five Agasicles intermean point distances. effects of both the subdivision of the samples into Among the vittate A^asic/^s species the phenoclinal three geographic forms and the increased variance distances between A. interrogationis and A. vit- resulting from the 1975 sample supplements. tata are the shortest, both for females and males Table 9 gives the total phenocline distances, as and for all 11 character pairs except PyW to PyL shown in figures 62-72, for the four vittate species (males only) and U2W to UIW. Since biogeographic of Agasicles and for the three fasciate forms of A. evidence indicates clearly that these two species are opaca. The sum of the distances taken up by the at opposite ends of a long series of geographic forms vittates for all character pairs comprises 70 percent (fig. 34), we must consider their apparent similarity of the overall Agasicles phenoclinal distances for to have resulted from evolutionary convergence. females and 59 percent for males. However, the Among the fasciate forms, the phenoclinal distance mean intermean point distances are relatively less, between the Paraguay River form and the Plains with only 60 percent of the sums for females and 49 of Mojos form oîAgasicles opaca is even less than percent for males. These results indicate that the that between A. interrogationis and A. vittata. But intermean point distances of the vittate forms are in this case, geographic contiguousness enables us greater, on the average, for females and subequal, to interpret phenoclinal proximity as indicating on the average, for the males as compared with true affmity. However, the closely related lower the fasciates. For each character pair, we also Amazon River form is widely separated pheno- present in table 9 the percentage of the total clinally, indicating wide divergence but with geo- Agasicles phenocline taken up by the vittate spe- graphic proximity and general similarity indicating cies. These percentages range from 54 to 86 for close affinity. the females and 49 to 70 for the males. These results In table 10, the female-to-female-plus-male per- show that the phenoclines for the vittates are longer centages, based on the totals both by intermean than those of the fasciates for all character pairs point distance and by character pair, do not show except for PrW to PrL and BL to BTh being a sexual dimorphism clearly. However, the two sets trifle shorter in the males. However, percentages of values for the obviously sexually dimorphic PyW based on the means of the intermean point distances to PyL do show the largest percentage of difference show that the vittates extend less than 50 percent of between females and males, though only by a small

100 Table 9.—Total second-version phenocline distances for vittate species of Agasicles and for geographic forms of fasciate A. opaca as shown in figures 62-72

Fasciate A. opaca Percent vittate Vittate A. hygrophila Character (Paraguay River form distance, A. hygrophila to A. vittata (mm) pair to Amazon River form) (mm) to A. opaca (lower (x to y) Intermean point Amazon River form) Total Intermean point (mean n=3) Total (mean n=2) Total Intermean point

FEMALES

PrW to PrL (fig. 62) 72 24 33 17 69 59 EL to EW (fig. m 49 16 38 19 56 46 BL to BTh (ñg. 64) 58 19 50 25 54 43 HW to HL (fig. 65) 47 16 20 10 70 62 low to lAW (fig. 66) 63 21 29 15 69 58 U2W to UIW (fig. 67) 166 56 60 30 74 65 AL to MTL (fig. 68) 67 22 11 6 86 79 4AL to 3AL (fig. 69) 81 27 30 15 73 64 6AL to 5AL (fig. 70) 105 35 33 16 76 69 7AL to7AW(fig. 71) 52 17 41 21 56 45 PyW to PyL (fig. 72) 133 44 44 22 75 67

Total 893 298 390 196 Percent 70 60 30 57 70 60

MALES

PrW to PrL (fig. 62) 59 19 61 31 49 38 EL to EW (fig. 63) 51 17 45 23 53 43 BL to BTh (fig. 64) 31 10 32 16 49 38 HW to HL (fig. 65) 24 8 23 12 51 40 low to lAW (fig. 66) 55 18 38 19 59 49 U2W to UIW (fig. 67) 163 54 43 22 79 71 AL to MTL (fig. 68) 71 25 49 25 59 50 4AL to 3AL (fig. 69) 70 23 68 34 51 40 6AL to 5AL (fig. 70) 97 32 58 29 63 53 7AL to 7AW (fig. 71) 68 23 62 31 52 43 PyW to PyL (fig. 72) 77 26 34 17 70 61

Total 766 255 513 259 — Percent 59 49 40 51 59 49 margin. Generally, the totals on which these per- tion. Seven of the eleven character pairs include centages are based obscure the sexually dimorphic from one to three percentages considered as indicat- changes that are usually localized in individual in- ing sexual dimorphism. Previously, we considered tervals of the phenoclines. A more definitive mea- phenoclines of four of these character proportions as sure of sexual dimorphism may therefore be the exhibiting sexual dimorphism (page 74). From the female percentage of the combined female and male standpoint of phenoclinal intermean point dis- distances between each of the phenoclinal mean tances, two intervals (Agasicles vittata to Paraguay points given in table 10. These percentages indicate River form of A. opaca and Paraguay River form to the differences in rates of change between females Plains of Mojos form of A. opaca) have no percent- and males for a particular interval of the phenocline ages considered as being indicative. A single inter- pair. We give these percentages separately in table val, Agasicles connexa to A. interrogationis, has 11 for females only and arbitrarily consider values two; another, A. hygrophila to A. connexa includes above 65 percent and below 35 percent as being three; and the Plains of Mojos to lower Amazon indicative of evolutionary trends that are sexually interval includes four. The largest number of per- dimorphic. In table 11 the indicative percentages centages considered to be indicative (six) occur are starred. They show a rather scattered distribu- within the Agasicles interrogationis to A. vittata

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102 interval. But these values are probably invalid because, as noted above and on pages 74 and 87, a more remote relationship between these two species may not allow them to be placed consecu- (A 0^ tively on an unbranched phenocline as represented by the first and second versions presented thus far. là Oí .3 ce -ri* (^ iO ^ lO (M^—'COLO Proposed trifúrcate S TJ c ?: s= ^ representation for the is phenoclines ofi oS Except along the eastern littoral and adjacent s (-) O) «3 C pjfi 4^ escarpments, Müller (1973) and Hafifer (1974) report

es o 'O o oooooocot-T^cTicoc^q^ no forested refugia in northeastern Brazil during *^ o the arid climatic periods of the Pleistocene (figs. 86 as g s i4_ O V £«2 o and 87). We also find a void in the distribution of e¿ O both alligatorweed and Agasicles across northeast- « àO fi CO Ö c« ern Brazil to Belém. For the vittate Agasicles äl^ species the hiatus continues to Georgetown and up •t^ g V. ^ the Amazon River beyond Hanaus. This wide sep- ^ 'S : eu .>; ^ aration between Agasicles interrogationis and A. CA S vittata is consistent with an out-of-line (switchback) fi ^ position for A. vittata on several phenoclines, most go« * * * * * * notably for two plottings: elytral length (EL) ^ S I .^ I against elytral width (E W) and the maximum width ^¡* w of the base of the black U-shaped elytral marking fi 0) (U2W, fig. 46) against the minimum width of the fi fi base of the ivory U-shaped elytral markings (UIW, fig. 46). The rather wide divergence between the ed (^ fi 4^ i 5 js -S fasciate forms of Agasicles and the vittate forms is evident in the contrast in configuration and color of their markings and by the wide separation between .S a ^ their points along the phenoclines generally. The Paraguay River form of fasciate Agasicles opaca t-j overlaps the range of vittate A. hygrophila and is V tf) fi allopatric with the two Amazonian forms. These

«« S; "O Ä- facts indicate that the Recent species of Agasicles do not constitute an unbranched phenocline or a Q -w ^_3 Ö5 closed circle of closely related forms but rather a trifúrcate series, shown diagrammatically in fig. 73. ^ Based on this representation, we present in figures 74-84 corresponding trifúrcate phenoclines for each of the 11 sets of character pairs consid- . î£) ÇD ^ ai o t> t- lo CD t- ered in the previous two sections. These third- u " g O ^^3 ""^ set is composed of a representation for the females o W PQ o 3 B ^ o o o S ^ bJD o -^^ O o Q ^J ,»J -l-J ^ í>. +J ^J (A) and for the males (B). For each phenocline the ■S Î> ^ C^ï ^ J HJ HJ ^ mean point of Agasicles hygrophila is the center H £ W PQ w 2;=) << Tt ço t> eu from which radiate the stem leading from Disonycha argentinensis (Da) and the three arms, each terminating in a mean point of an Agasicles species as follows: vittate A. vittata (Av), vittate A.

103 A. opaca Amazon River form

A. vittata A. opaca A. interrogo- Plains of Mojos form tiônis

A. opaco A. connexo Paraguay River form

A. hygrophila

Disonycha orgentinensis

FIGURE 73.-TVifurcate representation of relationship of existing Agasicles species. This scheme is consistent with the progression rule and the rule of deviation as proposed by Hennig (1966). The representation is superimposable upon existing geographical ranges. Although we proposed species I and II, we no longer consider them as unknown existing intermediate forms between Agasicles vittata Sind A. hygrophila. interrogation^ (Ai), and fasciate lower Amazon formed by the slopes of the stem and each of the River form of A. opaca (Aoa). arms and express degrees of divergence of one Figures 74-84 clearly show that, for all 11 charac- member with respect to the stem. The spread of ter pairs, the phenoclinal arm terminating in the angles is greatest for the character pair lOW to lower Amazon form of Agasicles opaca (Aoa) is lAW. It is least for the arms for 6AL to 5AL and significantly longer than the other two, denoting BL to BTh. In seven of the charts this spread tends much greater increase in size. The phenoclinal arm to be small for the three arms, indicating concor- terminating in vittate A. vittata (Av) is somewhat dance in evolutionary change. Striking changes in shorter to subequal to that terminating in vittate A. direction along the arms occur and may signify cor- interrogationis (Ai) except for character pairs PyW responding changes in evolutionary course, proba- to PyL (males only), AL to MTL, and 4AL to 3AL. bly in response to change in selection pressure. The phenoclinal stem leading from Disonycha Table 13 gives the phenoclinal distances for Re- argentinensis is shorter than the arms for the vit- cent vittate and fasciate A^asic/^s species as shown tate Agasicles except for three character pairs (in in figures 74-84. The distances for the fasciates order of decreasing magnitude): PrW to PrL, lOW remain unchanged from the previous representa- to lAW, and HW to HL. In table 12, we tabulate tions of the second-version phenoclines. However, the lengths of the stem and the three arms for in the third version, representation of Agasicles each character pair. Generally, the values for vittata as a separate arm increases the phenoclinal the Disonycha argentinensis stem are irregular distances for the vittate A^asic/^s for all character to discordant in comparison with the usual trend pairs except two. These are HW to HL and lOW to of increasing lengths proceeding from the Aga- lAW, and there is a decrease in these because of sicles vittata arm to the A. interrogationis arm the separate arms being slightly shorter than the to lower Amazon form of the A. opaca arm. The intervals of the second-version phenocline that totals for both females and males show more dra- they replace. matically this trend of increasing values among In the trifúrcate representation (table 13), the Agasicles and also the Disonycha argentinensis distances taken up by the vittates are longer for all stem as the shortest of the two sets of four totals. character pairs than those of the fasciates, ranging In figures 74-S4, another feature of the trifúrcate from 59 to 92 percent (average 75 percent) of the representation having the mean point of Agasicles total Agasicles phenoclinal distance for the females hygrophila as its center are the sizes of the angle of and 52 to 83 percent (average 69 percent) for the the stem and of the angles of radiation of the three males. The mean intermean point distances are not arms with respect to the stem. The angles are (Continued on page 117.) 104 fe fi ^ .2 ¡s a _S > (M 1«^ if-- -5 -^ "I .1 's s

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105 ö> c 0)

o C o

Pronotal Width

Aoa

O) c 0)

o c o

74 B

Pronotal Width

FIGURE 74.—Trifúrcate (third-version) phenocline for the mean points of pronotal width to pronotal length of flea beetles. A, Females. B, Males. This phenocline is at the same scale as that of the second version presented in figure 62. The mean point of Agasieles hygrophila is the center to which the stem leads fi*om Disonycha argentinensis (Da) and fi!*om which radiate the three arms, each terminating in a mean point of am Agasieles species as follows: vittate A. vittata (Av), vittate A. interrogationis (Ai), and fascia te lower Amazon River form of A. opaca (Aoa).

106 Aoa

HD o CÛ

75 A

Elytral Length

Aoa

■S

o CÛ

75 B

Elytral Length

FIGURE 75.—Trifúrcate (third-veráion) phenocline for the mean points of elytral length to elytral width of flea beetles. A, Females. B, Males. This phenocline is at the same scale as that of the second version presented in figure 63. The mean point of Agasicles hygrophila is the center to which the stem leads from Disonycha argentinensis (Da) and fi*om which radiate the three arms, each terminating in a mean point of SLU Agasicles species as follows: vittáte A. vittata (Av), vittate A. interrogationis (Ai), and fasciate lower Amazon River form of A. opaca (Aoa).

107 c0)

o Où 76 A

Body Length

c Aoq

"Ö O CO 76 B

Body Length

FIGURE 76.—Trifúrcate (third-version) phenocline for the mean points of total body length to body thickness of flea beetles. A, Females. B, Males. This phenocline is at the same scale as that of the second version presented in figure 64. The mean point of Agasides hygrophila is the center to which the stem leads from Disonycha arge7itive7isis (Da) and from which radiate the three arms, each terminating in a mean point of an Ai/as?W^s species as follows: vittateA. vittata (Av), vittateA. inferrogatiovis (Ai), and fasciate low^er Amazon River form of A. opaca (Aoa).

0> 0) c c I Aoa a> .^ ■o -o o o 0) X X .^--•Av 77A "^ 77B

Head Width Head Width

FIGURE 77,—Trifúrcate (third-version) phenocline for the mean points of head width to head length of flea beetles. A, Females. B, Males. This phenocline is at the same scale as that of the second version presented in figure 65. The mean point of Agasides hygrophila is the center to which the stem leads from Disonycha argentiiiensis (Da) and from which radiate the three arms, each terminating in a mean point oídiX\ Agasides species as follows: vittate A. vittata (Av), vittate A. interrogationis (Ai), and fasciate lower Amazon River form of A. opaca (Aoa).

108 o c c

78 A

Interocular Width

Aoa

o c c c o im

78 B

Interocular Width

FIGURE 78.—Trifúrcate (third-version) phenocline for the mean points of interocular width to interantennal width of flea beetles. A, Females. B, Males. This phenocline is at the same scale as that of the second version presented in figure 66. The mean point of Agasicles hygrophila is the center to which the stem leads from Disonycha argentinensis (Da) and from which radiate the three arms, each terminating in a mean point of an Agasicles species as follows: vittate A. vittata (Av), vittate A. interrogationis (Ai), and fasciate lower Amazon River form of A. opaca (Aoa).

109 I. cO- — ^ o

79 A

Maximum External Width of Elytral "U"

■o

Aoa

79 B

Maximum External Width of Elytral "U"

FIGURE 79.—Trifúrcate (third-version) phenocline for the mean points of maximum width of the base of the black U-shaped elytral marking to the minimum width of the base of the ivory-colored U-shaped elytral marking of flea beetles. A, Females. B, Males. This phenocline is at the same scale as that of the second version presented in figure 67. The mean point of Agasicles hygrophila is the center to which the stem leads from Disonycha arger^tinensis (Da) and from which radiate the three arms, each terminating in a mean point of an Agasicles species as foDows: vittate A. vittata (Av), vittate A. interrogationis (Ai), and fasciate lower Amazon River form of A. opaca (Aoa).

no o 15

= J

2 80 A

Antennal Length

o Aoa 15

o» ■£ « 80 B

Antennal Length

FIGURE 80.—Trifúrcate (third-version) phenocline for the mean points of antennal length to metathoracic tibial length of flea beetles. A, Females. B, Males. This phenocline is at the same scale as that of the second version presented in ñgure 68. The mean point of Agasicles hygrophila is the center to which the stem leads from Disonycha argentinensis (Da) and from which radiate the three arms, each terminating in a mean point of an Agasicles species as follows: vittate A. vittata (Av), vittate A. interrogationis (Ai), and fasciate lower Amazon River form of A. opaca (Aoa).

Ill c o E Aoa

o c c o c <

c o 81 A

Length of Fourth Antennal Segment

Aoa

o c c o c <

0)c o 81 B

Length of Fourth Antennal Segment

FIGURE 81.—Trifúrcate (third-version) phenocline for the mean points of lengths of fourth to third antennal segments of flea beetles. A, Females. B, Males. This phenocline is at the same scale as that of the second version presented in figure 69. The mean point of Agasicles hygrophila is the center to which the stem leads from Disonycha argentinensis (Da) and from which radiate the three arms, each terminating in a mean point of 3in Agasicles species as follows: vittate A. vittata (Av), vittate A. interrogationis (Ai), and fasciate lower Amazon River form of A. opaca (Aoa).

112 1 Aoa 0 c Ai «^ s 1 /x "o

c 0)

♦Da 82 A

Length of Fifth Antennal Segment

c E

"5 c

c <

O) c 0)

82 B

Length of Fifth Antennal Segment

FIGURE 82.—Trifúrcate (third-version) phenocline for the mean points of lengths of sixth to fifth antennal segments of flea beetles. A, Females. B, Males. This phenocline is at the same scale as that of the second version presented in figure 70. The mean point of Agaskles hygrophila is the center to which the stem leads from Disonycha argentinensis (Da) and from which radiate the three arms, each terminating in a mean point of an Agasides species as follows: vittate A. vittata (Av), vittate A. interrogationis (Ai), and fasciate lower Amazon River form of A. opaca (Aoa).

113 c 0) E O) o CO

c c 0) c < c > CO

83 A

Length of Seventh Antennal Segment

c 0) E O) 0) V) "5 c c c <

83 B

Length of Seventh Antennal Segment

FIGURE 83.—Trifúrcate (third-version) phenocline for the mean points of length to width of seventh antennal segment of flea beetles. A, Females. B, Males. This phenocline is at the same scale as that of the second version presented in figure 71. The mean point of Agasicles hygrophila is the center to which the stem leads from Disonycha argentinensis (Da) and from which radiate the three arms, each terminating in a mean point of an Agasicles species as follows: vittate A. vittata (Av), vittate A. interrogationis (Ai), and fâsciate lower Amazon River form of A. opaca (Aoa).

114 Aoa

ö> c

84 A

Pygidial Width

c 0

Aoa

84 B

Pygidial Width

FIGURE 84.—Trifúrcate (third-version) phenocline for the mean points of pygidial width to pygidial length of flea beetles. A, Females. B, Males. This phenocline is at the same scale as those of the second version presented in figure 72. The mean point of Agasicles hygrophila is the center to which the stem leads from Disonycha argentinensis (Da) and from which radiate the three arms, each terminating in a mean point of an Agasicles species as follows: vittate A. vittata (Av), vittate A. interrogationis (Ai), and fasciate lower Amazon River form of A. opaca (Aoa).

115 Table IS.—^Total third-version phenocline distances for vittate species of Agasicles and for geographic forms of fasciateA. opaca as shown in figures 74-84, illustrating the trifúrcate phenocline representation [Millimeters]

Fasciate Vittate A. vittata to A. interrogationis A. opaca (Paraguay A. vittata to -\- A. opaca (Paraguay River form Character River form to A. interrogationis to lower Amazon River form) pair lower Amazon River form) (xtoy) Total Mean Total Percent distance Total Mean distance (n=3) distance of vittate Aörcusic/e.s distance (n=2)

FEMALES

PrWtoPrL(fíg.74) 96 32 33 17 129 74 EL to EW (fig. 75) 85 28 38 19 123 69 BLtoBTh(fig.76) 72 24 50 25 122 59 HWtoHL(fig. 77) 44 15 20 10 64 69 low to lAW (fig. 78) 60 20 29 15 89 67 U2WtoUlW(fig.79) .... 208 69 60 30 268 78 AL to MTL (fig. 80) 128 43 11 6 139 92 4ALto3AL(fig.81) 131 44 30 15 161 81 6ALto5AL(fig.82) 163 54 33 16 196 83 7ALto7AW(ñg.83) 70 23 41 21 111 63 PyWtoPyL(fig.84) 185 62 44 22 229 81

Total 1,242 414 390 196 Percent 75 68 25 32

PrWtoPrL(fig. 74) 145 48 61 31 206 70 EL to EW (fig. 75) 95 32 45 23 140 68 BL to BTh (fig. 76) 61 21 32 16 93 66 HWtoHL(fig.77) 30 10 23 12 53 57 low to JAW (fig. 78) 41 14 38 19 79 52 U2WtoUlW(fig. 79) .... 214 71 43 22 257 83 AL to MTL (fig. 80) 124 41 49 25 173 72 4AL to 3AL (fig. 81) 121 40 68 34 189 64 6AL to 5AL (fig. 82) 181 60 58 29 239 76 7ALto7AW(fig.83) 96 32 62 31 158 61 PyWtoPyL(fig.84) 104 35 34 17 138 75

Total 1,212 404 513 259 Percent 69 60 31 40

116 so much longer in the case of the vittates, with ellipses in showing that there has been less di- values of 68 percent for females and 60 percent for vergence among the fasciate forms than among the males. However, these results show clearly that vittate Agasix^les forms. This evidence substan- the mean intermean point distances of the vittate tiates our view that the three fasciate Agasicles species average greater for both females and males. forms are subspecific forms of a polytypic species For each character pair, we also present in table 13 rather than semispecies of a superspecies as in the the percentage of the total Agasicles phenocline vittate Agasicles species. With these taxonomic taken up by the vittate species. The percentages concepts, we may make the following interpreta- range from 63 to 92 for the females and from 52 to 83 tions: Having undergone most of its evolution infor the males. These results show that the total teracting with small-stemmed alligatorweed (and phenoclines of the vittates are longer than those of its ancestral forms), fasciate polytypic Agasicles the fasciates for all character pairs. However, per- opaca diverged from the vittate forms, continuing centages based on the means of the intermean point its evolution interacting mostly with oversized distances show that the vittates extend less than 50 stems of Alternanthera hassleriana. While this re- percent of the distance along the Agasicles pheno- lease from the interaction with small stems relates cline for a single character pair, BL to BTh (49 per- to an accelerated rate of divergence from the vittate cent), in the females and two character pairs, HW to forms, it also relates to slowed evolution of repro- HL (45 percent) and lOW to lAW (42 percent), in ductive isolation and therefore speciation among the males. These results show that both the total the fasciate forms. Conversely, if the speciation phenoclinal distances and the intermean point dis- rate is greater with more intensive host-plant-stem tances of the vittate species are greater than those and flea-beetle interaction, we may conclude that of the fasciate forms for almost all character pairs progress of the taxon cycle depends primarily upon for both females and males. In the third-version coevolutionary processes in Agasicles, In such in- phenoclines as compared with those of the second stances, counterevolutionary and coevolutionary version (p. 100), the lead of the vittates increases processes could be, at least in part, one and the over the fasciates in the distance each takes up same. However, the evidence of our study indicates along the Agasicles phenocline. We consider this that the host plant, Alternanthera hassleriana^ increase in the distances of the vittates as indicating was advanced in its evolution when Agasicles a truer representation of the evolutionary history appeared and may have changed very little struc- oí Agasicles. turally as the Agasicles species diverged and These third-version phenoclines more than the speciated geographically without resort to second versions complement the normal bivariate resource partitioning.

117 SUMMARY AND CONCLUSIONS

The interaction between host-plant stem and and their normal ellipses to the single mean point Agasicles pupation is unique among the Chrys- and ellipse of the combined samples of fasciate A. omelidae. The specialized compartmentalized hol- opaca. The stem of the unbranched phenocline ex- low stem of the amphibious amaranths may also tends from the mean point and normal ellipse for be unique among both aquatic and terrestrial Disonycha argentinensis. The second-version plants. In Agasicles y many marked structural mod- phenocline is essentially the same as the first ver- ifications have resulted from the interaction which sion except that calibration errors are corrected and are remindful of ecological-morphological relation- the samples of the fasciate polytypic A. opaca are ships existing in the stem-boring Buprestidae and divided into three geographical components, with Cerambycidae (Hespenheide 1969). However, the the result that a series of three mean points and paired T-shaped "cremaster" of the pupa is unique, their normal ellipses replace the single mean point and the remarkable sexually dimorphic external and ellipse of the first version. In the third version, genitalia seem to have arisen de novo and been the mean points are reordered, and the phenocline important directly in the differentiation within the assumes a trifúrcate form that corresponds to genus. Apparently indirectly, interaction with the the trifúrcate distribution of the seven forms of host-plant stem has been instrumental in the specia- Agasicles in nature. The stem, as in the first and tion of Agasicles. However, there is no evidence second versions, extends from the mean point of that any of the forms of Agasicles has speciated by Disonycha argentinensis. Additionally, we have resource partitioning, that is, by dividing up the considered the three normal host plants of Aga- habitat in the form of a common host plant. This lack sicles in South America, namely, alligatorweed, of habitat subdivision accounts for the allopatry and Altemanthera hassleriana, and A. sessilis. parapatry within Agasicles that have resulted in The stem diameters of Altemanthera sessilis marked reduction in range and therefore advance- tend to be undersized for pupating Agasicles y while ment along the taxon cycle. No speciation is appar- those of alligatorweed tend to be slightly oversized. ent in the other recognized specialized biotic agents Those of Altemanthera hassleriana are markedly of amphibious amaranths, which, like Agasicles^ oversized. The large size of the fasciate Agasicles have geographic ranges that are nearly coextensive species is clearly related to the large stem size of with that of alligatorweed in South America. These its host plant. The somewhat smaller size of the include Vo^^m malloi axid Amy nothrips andersoniy Paraguay River form of fasciate A. opaca may be both of monotypic genera, and the leaf-mining related to a partial dependence mostly in transition Agromyza alternantherae and Disonycha argen- zones upon the smaller stemmed host, alligator- tinensisy both of large polytypic genera. We reiter- weed. The overall small size of the vittate species of ate that in D. argentinensis there is no interaction Agasicles is related to the smaller stem size of their of host-plant stem and flea beetle. host plants, alligatorweed and Altemanthera We have considered in detail four vittate species sessilis. However, we have no evidence that the and three subspecific fasciate forms of Agasicles progression in size in the vittate species from and the close extrageneric relative, Disonycha Agasicles hygrophila to A. interrogationis and from argentinensis. For these South American dis- A. hygrophila to A. vittata is related to stem di- onychine flea beetles, we have presented three dif- ameters. Contrary to Bergman's rule, there may ferent versions of the phenoclines for 11 sets of be instead a meaningful relationship both in vittate character pairs. The first version extends through and fasciate Agasicles species of increasing insect mean points of the four vittate species of Agasicles size with increasing tropical climate and increas-

118 ing period since divergence from the ancestral der ascending stems of A. sessilis. We also see form(s) of A. hygrophila, the smallest species. stem-diameter reduction of alligatorweed in the Later (p. 126), we will consider another possible form of regeneration in an area denuded by Agasi- explanation for the small size of A. hygrophila. cles. Additionally, we see the length of the ascend- With respect to mean points for character pairs, ing portion of the stem related to its basal width. the phenoclines show that, of the seven forms of Our field observations show that the forms of Agasicles, A. hygrophila falls closest on the av- Agasicles occur allopatrically to parapatrically, or erage to amphibious-amaranth-oriented Disonycha rather broadly sympatrically in the case of the argentinensis. These results are consistent with Paraguay River form of fasciate A. opaca and vit- zoogeographical, morphological, and biological con- tate A. hygrophila. Also, as we found them occur- siderations and indicate the probable extrageneric ring in the field, we show the four vittate species as relationship between D. argentinensis and A. hy- a group interacting with alligatorweed as well as grophila. However, without the important back- Agasicles vittata interacting alone, over part of its ground information, much of this proximity might range, with Alternanthera sessilis. Similarly, we be considered simply as coincidence resulting from show the ÎBScisite Agasicles species interacting with similarity of body and appendage size. Host-plant Alternanthera hassleriana. In each case, we show and biogeographical information further indicates flea beetle size interacting with host-plant stem affinities among Disonycha argentinensis, D. col- diameter. But because of the limitations of our sam- lata, D, xanthomelaSy and D. glabrata. Important pling, we have not related each species of Agasicles in establishing relationship may be the transference with its particular host within the limits of its par- of North American D. collata and D. xanthomelas ticular geographic range. to alligatorweed, a disjunct host plant for these flea Of the graphical representations for the flea bee- beetles. Also important may be the adult-limited, tle characters, pronotal width related to pronotal disjunct orientation to alligatorweed of Western- length most clearly shows a positive relationship Hemisphere-wide Z). glabrata, observed and tested with diameter of the host-plant internode in which in North America but to date not found to exist in Agasix^les pupation occurs. In contrast, pupation of South America. most other flea beetles occurs in a cell formed by the The more slender-stemmed Alternanthera ses- prepupa in the soil, and the pronotum may be broad silis does not occur within the range of small-sized and short, as it is shown for Disonycha argentinen- Agasicles hygrophila. But this plant is an alterna- sis. Elytral length related to elytral width and total tive host of Agasicles connexa and A. interroga- length of body related to thickness of body show this tionis along the east coast of Brazil. It is probable relationship with stem diameter less clearly. Head that this plant invaded the range of both of these width related to head length is more erratic in flea beetles after each had undergone its evolution trend, and interocular width related to interan- on alligatorweed. Also, Alternanthera sessilis sup- tennal width is even more so. The last two sets of ports the intermediate-sized Agasicles vittata ex- character pairs include widths that do not nor- clusively over part of the flea beetle's range. This mally contact the restrictive walls of the host- insect probably reached this acceptable host plant plant internode. Therefore, these widths probably by coincidence after having undergone most of its are quite free to diverge or converge. A slen- evolution on alligatorweed and its ancestral forms. der prothorax and narrowed head result in the In the rain forest conditions of the sub-Andean increased mobility of these structures that is ap- ranges and possibly along the east coast of Brazil, parently needed for in-stem feeding and exit- occurrence of this host plant must be widely sepa- hole-making by the newly emerged flea beetle. rated because of its dependence on tree falls for Other character pairs have phenoclines that openings in the canopy. This sparse distribution of seem to be related to the increases in general host plant may tax the searching ability of the de- body size of the flea beetle species. Included here pendent insect. Thereby, development of plants of are the relations of antennal length to metathoracic full size may be allowed before arrival of the sup- tibial length, fourth to third antennal length, and pressive insect. (However, see p. 13.) sixth to fifth antennal length. Still another class of From the normal ellipses we see the conspicu- character pairs is represented by a single trend line, ously inflated internodes of decumbent stems of length to width of seventh antennal segment. It Alternanthera hassleriana, the more or less slen- may indicate evolution of slightly more slender der ascending stems of alligatorweed, and the slen- appendages in the vittate species of Agasicles,

119 followed by more robust appendages in the fas- are the relations between the widths of the bases of ciate species that pupate in more spacious inter- the concentric U-shaped elytral markings and be- node cavities. tween the width and length of pygidium. Another class of character pairs expresses the By means of the bivariate normal ellipses, diag- variation of elytral markings. Our single example nostic taxonomic discrimination is demonstrated for also seems to express the elongation of the apical Agasicles hygrophila (fig. 55) and for the combined region of the elytra by the widths of the bases forms of A. opaca (figs. 50, 51, 53-55). Partial tax- of the concentric U-shaped elytral markings. This onomic discrimination is demonstrated for A. inter- elongation may be related to the elongation and rogationis females and A. vittata females (fig. 60A). development of the female pygidium into an exter- Except for the character pronotal length to width nal genitalic "key." However, there is no conspicu- (fig. 50), the normal ellipses for Disonycha argen- ous discordance between the pair of phenoclines to tinensis are either superimposed upon or else indicate sexual dimorphism. Possibly the corre- widely overlap those of the vittate species of Agasi- sponding development of the "key" in the female cles, As compared with the vittates, none of the and the "lock" in the male cancels out much of the three fasciate forms are separated by means of the discordance between the sexes in the elytral apices normal ellipses, even though their intermean point and their associated markings. intervals change direction markedly. Usually, it is The phenoclines are strikingly discordant be- small intermean point distance and broad, large tween the females and the males for the relation of ellipses that decrease taxonomic discrimination. width to length of pygidium. This discordance is Along the second-version phenoclines the totals of clearly a result of sexual dimorphism and reflects distances of the fasciates are less than most of those the development of the external genitalic key in the of the vittates. The differences are even greater females, in contrast with the miniscule development along the third-version phenoclines. On the basis of of this structure in the male. With all the diversity the differentiation of their external lock-and-key of the 11 sets of evolutionary trend lines presented genitalia, of their uncleared aedeagi, and of their in this study, there is general concordance between elytral markings, we consider the four forms of the sexes except for this obviously dimorphic pair. vittate Agasicles as probably reproductivejy iso- A corresponding pair based on the development of lated. Since these forms are geographically ex- the external genitalic lock in the male contrasted clusive and are so similar ecologically, we further with the female was not possible because of the consider them as being semispecies of a superspe- absence of corresponding landmarks in most fe- cies (Amadon 1966; MacArthur 1972; Haffer 1974). males. Less obvious sexual dimorphism does oc- On the other hand, we have not been able to sort cur in various character pairs. We consider that the three forms of fasciate Agasicles opaca on the female percentages of the combined female and basis of uncleared aedeagi^ external lock-and-key male distances between each of the second-version genitalia, or meaningful discrimination by normal phenoclinal mean points indicate sexual dimorphism ellipses. In view of these facts and the phenoclinal at one to three separate intervals for each of seven distances being generally shorter in the fasciates as character pairs besides the one relating width to compared with the vittates, we consider the three length of pygidium. fasciate Agasicles forms as being subspecific forms In most graphs of correlation between flea beetle of polytypicA. opaca (Mayr 1970). characteristics, there is maximal intercharatter Although the unbranched first- and second- correlation because there is consistent alinement of version phenoclines provide a consistent successive the normal ellipses, with only a very occasional el- order for the mean points of the character pairs, lipse showing significant rotation from the norm. they provide only limited evidence of the evolution- Both the vittates and fasciates show this tendency. arily significant geographical separation between For a few pairs of characters, however, there is Agasicles vittata and A. interrogationis, The diverse orientation of the ellipses; and, in such switchback in direction that occurs in a few of the cases, there is usually a reduction in the amount of phenoclines between the mean points for these two overlapping, especially if there is a sufficient inter- species may be important evidence if viewed from val between the mean points along the phenocline. the standpoint of possible parallel evolution. But In these there is low intercharacter correlation, a the importance is open to question because of simi- high level of discrimination, and, therefore, utility lar switchbacks occurring along the same pheno- as taxonomic characters. Most notable among them clines between geographically proximate Paraguay

120 FIGURE 85.—Recent distribution of rain forests (crosshatched) and open landscapes (blank) in the Neotropics. (From Müller 1973, reprinted by permission of Dr. W. Junk b.v. Publishers.)

River and Plains of Mojos forms of fasciate Aga- as compared within the fasciates. Biogeographi- sicles opaca. However, the limited evidence bear- cal evidence supporting the trifúrcate form of the ing on whether A. vittata has closer affinities phenocline follows. with A. hygrophila or with A. interrogationis is Six of the seven forms of Agasicles are known to consistent with extensive biogeographical evidence infest alligatorweed, and the four vittate species are for a wide void between the ranges of A. vittata known to depend either principally or exclusively and A. interrogationis. Therefore, we consider that upon this single host plant within their native the Recent Agasicles species do not constitute an ranges. These four species seem to be equally unbranched line or a closed circle of closely related specialized geographic forms suppressing the same forms but rather a trifúrcate series (fig. 73). We species of host plant. One of them, Agasicles hy- have applied this concept in reordering the mean grophila, is the most primitive structurally, and points for the third-version phenoclines of the 11 we consider it the least geographically derived; i.e., sets of character proportions. In this third version, the most primitive member of this genus occurs ei- the lead of the vittates increases over the fasciates ther within or adjacent to the region of longest his- for the distance each takes up along the Agasicles tory of habitation. The other three are the more phenocline. This greater phenoclinal distance indi- structurally and geographically derived A. con- cates more advanced speciation within the vittates nexa and A. interrogationis of the Brazilian east

121 .«^^^ ^^^^ -"^^

FIGURE 86.—Distribution of presumed forest refugia in the Neotropics during dry climatic phases of the Pleistocene, based upon Recent occurrences of three diverse animal groups. Left, neotropical bird distributions (Haffer 1974). Center, Amazonian lizards, Anolis chrysolepis species group, distributions (Vanzolini and Williams 1970). Right, Heliconius butterfly distributions (Brown et al. 1974). (From Haffer 1974, reprinted by permission of the Nuttall Ornithological Club.) coast, and, in another direction, A. vittata. Alter- distribution of alligatorweed but apparently not in nanthera sessilis occurs in the range of each of the case of the amphibious sunsranthAlternanthera the three species and is an occasional to exclusive reineckii. However, we have no evidence that there host plant. was any exchange, either of forms of Agasicles or of Except for those endemic to the region, many forms of amphibious amaranths, across the pres- plant and animal species of the Atlantic coastal ently unforested central tablelands separating the forest (the east Brazilian forest shown in fig. 85) Amazonian forest and the forests of southeast have their closest relatives in the Amazonian rain Brazü (Smith 1962; Haffer 1974). We know, of no forest (Smith 1962; Müller 1973; Haffer 1974). In rain-forest connections across northeastern Brazil comparing figures 34 and 85, we find this similarity being shown by any author. One may also consider very unlikely in the case of Agasicles connexa and Agasicles and alligatorweed as having a maritime A. interrogationis, which we judge to be more distribution pattern along the Atlantic coast of closely related to A. hygrophila of the lower basin of Brazil. But as Smith (1962) points out with respect the Rio de la Plata. From figures 1-6 and the to plants, migrations have been from the north phenoclines, wittaiè Agasicles vittata of the upper rather than from the south. Amazonian forest region and.fasciate A. opaca of Figure 85 shows the Recent distribution of the lower Amazon Basin are by the principle of forests and open formations in South America and parsimony clearly more distantly related than A. Central America. Figures 87 and 88 show the hygrophila is to the two Atlantic coastal forms of forested and nonforested dispersal centers as con- Agasicles, For possible comparison with these ceived by Müller (1973), and figure 86 shows the biogeographical relationships in Aga^i^les, we note distribution of presumed forest refugia during dry the invasions of vertebrate species of the Uru- climatic phases of the Pleistocene as considered by guayan dispersal center (fig. 86) into the Atlantic Haffer (1974). In comparing each of these distribu- forest of southeast Brazil as reported by Müller tions with those of Agasicles species given in figure (1973). We also note Smith's (1962) representations of the migration of plants from the Paraguayan 34, we see that A. hygrophila y the most primitive forest areas. To reach the Atlantic coastal forests, species, extends either along the edges of or only these plants cross over the Mesozoic basaltic shield, shallowly into three of MüUer's (1978) nontorest which we have found to be mostly a void in the dispersal centers, viz., the Uruguayan center (35),

122 FIGURE 87.—Rain forest dispersal centers of terrestrial vertebrates in the Neotropics. Montane forest centers are shown by fine hatching and the lowland forest centers by coarse hatching. (From Müller 1973, reprinted by permission of Dr. W. Junk b.v. Publishers.) the Pampa center (38), and the Chaco center (36).^^ ceived by Müller (1973) and again, but differently, We find further that the existing range of Agasicles by Haffer (1974). In addition, we find that Agasicles vittata includes several rain-forest refugia con- connexa and A. interrogationis might relate to the southern subcenter and the two combined northern ^We need to point out that while these 3 dispersal centers are subcenters respectively of the Serra do Mar réfugia represented as being nonforested, gallery forest commonly oc- of the Atlantic coast of Brazil (Haffer 1974). Al- curs in them along the banks of fluvial systems. Smith (1962) though we do not show a map of them. Mulleras refers ^to the complex of gallery forests of the basin of the Rio de (1973) Paulista subcenter and Bahia combined with la Plata as Paraguayan rain forest. In comparison with the the Pernambuco subcenter are even more compa- Amazonian rain forest, he further considers "the Paraguayan Basin [as] having developed a flora of its own to an even greater rable with the ranges of the two Atlantic coast extent than has the [Atlantic] coastal rain forest." We consider Agasicles species. the southwestern portions of the southeastern Brazilian forest This study shows that the unusual body form of shown in fig. 85 as constituting the areas of more continuous Agasicles has developed largely as a result of a cover of the Paraguayan rain forest. We found outliers of it process of conformation to the host-plant stem in across Corrientes Province to the lower Paraná River. Also, we which pupation takes place. The three fasciate need to point out that Müller (1973) considers his Pampa center (38) to have much in common with his Uruguayan center. coccinellid-mimicking forms of A. opaca are more The endemic fauna of both centers is adapted to an unfor- geographically derived species that developed in ested landscape. large stem cavities after a process of conformation

123 FIGURE 88.-Nonförested dispersal centers of terrestrial vertebrates in the Neotropics. Agasicles hygrophilajnd ^Uigatorweed occur alone the eastern margins of centers 36 and 38 and the western, southern, and eastern margins of center 35 (see figs, áb and a»), A. opaca and A. vittata do not quite reach the northwest margin of region 36 (see fig. 38). (From Müller 1973, repnnted by permission of Dr. W. Junkb.v. Publishers.) to slender stems had been achieved. All three forms alligatorweed from exclusively terrestrial ancestral have room to spare when pupating in their principal forms. Previous to this process of adaptation and host plant, Alternanthera Imssleriana. The over- speciation and possibly contemporaneous with the sized stem of this plant and the absence of small- evolution of alligatorweed from a terrestrial to an stemmed regeneration that might be restrictive to amphibious plant, A. hygrophila and its precursors Agasicles may constitute important evidence that diverged from their ancestral form near Disonycha the ancestral form of the Paraguay River form argentinensis. This step probably occurred before found the ancestral form of Alternanthera has- the Pleistocene in the basin of the Rio de la Plata. sleriana with stem diameters approaching those It is conceivable how the Pleistocene may well existing today. Alternatively and possibly co- have played an important role in the speciation of evolutionarily, the flea beetle could have in- Agasicles. Consider the very recent formation of creased in size as the host-plant stem increased in the lower Amazonian deltaic plain. Consider the diameter. Then, the plant stem continued to in- probable isolating effects of the dry climatic phases crease beyond the requirements for accommodation of the Pleistocene upon the Plains of Mojos and the of the pupating insect. In the case of the vittate forests of the Bolivian jungas with respect to the species of Agasicles, our evidence neither proves or upper Paraguay Basin. Consider the possible isolat- disproves the possibility of their coevolution with ing effects of the changes in eustatic level in the

124 estuarine Río de la Plata and along the eastern coast lowed a splitting up of the populations. In addition of South America. Consider the possible isolating to the contraction and expansion of forest refugia, effects of the colder climatic phases in the region of interglacial seas engulfing the lower Paraná River the lower Rio de la Plata. Consider the effects of the and transgressing portions of the exposed Conti- dry climatic phases upon the integrity of the coastal nental Shelf of the craggy east coast of Brazil could rain forest. Then consider the present geographic have formed barriers and obliterated habitats for ranges of the seven forms of Agasicles. Consider alligatorweed and its insects. During glacial ad- further the two probable ancestral forms of the vances the ancestral form near Agasicles hygro- three subspecific forms of A. opaca: that of the phila may have resorted to refugia as far north as Paraguay River form of A. opaca and A. hygro- the Pantanal and the upper Paraguay River. In this phila; that of A. vittata and A. hygrophila; that way, the flea beetle ancestral forms may have be- of A. hygrophila and A. connexa; and that of A. come associated with and become adapted to connexa and A. interrogationis. The relationship Alternanthera hassleriana or its ancestral form. within the first set of three and within each of the Possibly climatic change, such as increasing aridity, last two sets is especially Hkely, considering the could have separated the population of the refugium close affinities within the first three and the last from that portion which repopulated the southern three existing forms and considering the similarity coastal regions. In this way, fasciate Agasicles of their ecological niches and their adjacent geo- opaca could have originated. Similarly, the ances- graphical distributions. Consistent with this con- tral forms of Agasicles vittata could have been cut ception, Müller (1973) summarizes numerous off, as they are now, during periods of greater or well-documented examples of subspeciation in ver- less aridity, from the range of the more primitive A. tebrates that clearly took place in glacial times.^'^ hygrophila and its ancestral forms. The existing With these examples in mind it seems clear that more primitive species, A. hygrophila, presently the first changes in the differentiation of Agasicles occupies a range that is central to all three branches probably occurred in the form of geographic varia- of the dendrogram (fig. 73) which is superimposable tion of a wide-ranging species. There probably fol- upon the Recent pattern of geographical distribution of Agasicles, This trifúrcate superimposability takes on added significance in view of our knowl- 2''Müller (1973) states: "For polytypic species with monocen- edge of dispersal capability, niche-space limits and tric subspecies, it can be shown that the dispersal centers represent centers where terrestrial vertebrates were preserved niche-saturation capacity that characterize the [survived] during regressive phases of the environment; i.e., component forms of Agasicles. In view of this back- they [dispersal centers] have acted in the past as refuge areas." ground the speculations just given may be con- Even more cogent for comparison with our picture of Agasicles sistent with Darlington's (1970) concept that the may be Haffer's (1974) conclusions: "A high percentage of neo- primitive member(s) of a species complex occur tropical birds are members of superspecies, e.g., 76% of the jacamars (Galbulidae) and 85% of the toucans (Ramphastidae). more Hkely in the region of less stable ecology; that Probably, écologie competition is an important factor in deter- is, the temperate to subtropical region just south of mining the range limit of numerous allied bird species in South the Tropics. However, the question remains: Has America. I suggest that the component species of each super- this southern region been any more climatically un- species originated from a common ancestor whose range was stable than the Tropics which apparently alternated fragmented through vegetational changes during adverse climatic periods of the Quaternary. The 'sister' populations inhab- between wet and dry periods (Müller 1973; Haffer iting the various 'refugia' deviated at differing rates from their 1974)? On the other hand, we think it is untenable to ancestor, and from each other, by selection and chance. consider the three terminal forms of the trifúrcate Upon the return of more favorable climatic and vegetational phenocHne as representing more primitive forms. It conditions newly developed forms came into secondary contact seems obvious from this study that they are the with varying results, according to which stage had been reached in the speciation process, viz., more or less extensive three most derived forms. hybridization, geographic exclusion with no or only very limited Subaquatic insects such as Agasicles are asso- hybridization, or range overlap of varying extent, if sexual ciated primarily with drainage systems—their al- as well as écologie compatibility had been attained during the luvial plains, lagoons, and deltas. It may seem that previous period(s) of ecologic-geographic isolation. Zones of they would be little affected by fluctuating wet to secondary contact between Amazonian forest birds reveal striking faunal discontinuities in a continuous forest environ- dry periods of the Pleistocene. But, in view of the ment. Areas of faunal fusion in Middle America and Amazonia dependence of the vit täte species upon shade or fall between postulated forest refugia and are characterized by cloud cover (low evaporation rates), and rainfall, for clusters of contact zones of species and subspecies pairs." population increase, forest refugia may have played

125 an important role in the speciation of these forms. rogationis. Alternatively, it is possible that all bar- The present range oîAgasicles vittata (fig. 34) coin- riers came into existence simultaneously, and the cides with Müller's (1973) and Haffer's (1974) ea^t successively increasing degrees of divergence Peruvian presumed forest refugia (figs. 86 and 87). among the vittate species of Agasicles could simply Likewise, the ranges of A. connexa and A. inter- reflect gradients of increasing tropical climates of rogationis coincide with southern and northern pre- both Recent and earlier times. These vittate species sumed forest refugia of the Serra do Mar. Also, in presumably underwent their evolution principally the lower Mississippi Valley region, we have found on alligatorweed and its ancestral forms. Appar- that during cold to hot-dry years introduced ently, no intermediate forms between Agasicles Agasicles hygrophila is unable to disperse north- vittata and A. hygrophila exist except possibly ward from its permanent population centers along as fossils. the Gulf of Mexico coast. In contrast, remarkable dispersal occurs during cool to warm-moist years The somewhat different course of evolution of the (Vogt et al., cited in footnote 20). three forms of fasciate Agasicles opaca took place Apparently because of their being close to the on a different host plant, Altemanthera has- water surface on nonascending Altemanthera hassleriana and its ancestral forms. Again the pheno- sleriaruiy which has an additional feature of water- clines show that the geographically most remote cooled stems, the fasciate forms of Agasicles are form of Agasicles (lower Amazon River form) is tolerant of insolated habitats. It may be that vittate clearly the most derived. However, prior to the A. hygrophila and possibly A. vittata, which should appearance of the ancestral form of Agasicles respond positively to these same features, are opaca, ancestral alligatorweed probably had competitively excluded by the fasciate Agasicles evolved to the more specisilized Altemanthera has- species. Mimicry of its aposematically marked sleriana as an adaptation to the hydrographie flux predator, Coleomegilla quadrifasciata, may be an of river lagoons and seasonally flooded lands such as important factor favoring the fasciate Agasicles the Plains (Llanos) of Mojos. We assume that soon over the vittate forms in insolated lagoons. The after its divergence from ancestral Agasicles hygro- vittates may be more subject to prédation by birds phila in the upper basin of the Paraguay River the such as the widespread jaçana that characteristic- ancestral A. opaca increased markedly in size and ally range over the insolated lagoons and backwa- invaded the Amazon Basin by way of the Plains of ters. In the transition zone adjacent to the habitats Mojos to become the ancestral lower Amazon River of Altemanthera hasslerixina, Agasicles hygro- form, which continued to diverge. Presumably, the phila and possibly A. vittata coexist on alligator- course of migration of the ancestral forms of weed with the Paraguay River form and possibly the Agasicles vittata followed along the forested base of Plains of Mojos form of A. opaca because of better the Andean foothills apart fi^om the insolated Plains adaptation of the vittate species to alligatorweed. of Mojos. Like the route along the east Brazilian On the alligatorweed side of the transition zone, the littoral, this route of migration is transverse to the larger sized fasciate Agasicles species are less drainage courses reaching down from the adjacent favorably accommodated by smaller host-plant mountains (flg. 34). stems. Possibly, this interspecific competition has Beyond its initial phases, the wide divergence selected for small size in Agasicles hygrophila. between Agasicles hygrophila and the Paraguay None of the other vittate Agasicles is subject to a River form of fasciate A. opaca probably occurred comparable competitive situation. Therefore, there in situ, i.e., patristically or phyletically, with no may be greater freedom for their size increase. surviving intermediate forms. In the case of the The courses of the phenoclines for the vittate vittate species A. vittata, it has been supposed that species of Agasicles suggest that a first step in the one or two unknown species near its ancestral form differentiation of the three species occurring along existed in the sub-Andean region extending from the eastern coast of South America could have been southern Peru to northern Argentina. These spe- the splitting off of A. interrogationisy followed at a cies were considered as being intermediate in later period by the splitting off of A. connexa. The form between A. vittata and A. hygrophila (flg. 73). still more derived character of A. vittata indicates However, this possibility faded with the finding of that it would have split off earlier from the ancestral Agasicles vittata north of Santa Cruz (Portachuelo), form of Agasicles hygrophila than did A. inter- Bolivia, and the finding of oligophagy (stenophagy)

126 within Alternanthera of Disonycha argentinensis we believe Agasicles could have lost winter hardi- (Vogt and Cordo 1976). ness as a tradeoff in evolving strong hygrophil- Considering its subgeneric distinctness, its ous responses.2^ tropicopolitan distribution, and the rather Hmited We interpret the findings of this study as being geographic area where it alone is attacked by a consistent with the center of origin and progression specialized species of Agasicles y it may be that an rule of Hennig-Brundin as discussed by Hennig important indigenous center of Alternanthera ses- (1966), Darlington (1970), Brundin (1972), Briggs silis is in the sub-Andean region of the Amazon (1974), and Ball (1975). Basic to this consideration Basin. However, as already indicated, Agasicles are the closely comparable specializations of each of vittata or its ancestral form probably reached this the four vittate species and each of the three fas- plant by coincidence in the course of its migration, ciate forms of Agasicles. Additionally, there are the after having undergone most of its evolution on niche-saturation capacity, dispersal capability, and Alternanthera philoxeroides and its ancestral geographic exclusion characteristic of each of the forms. Over its entire worldwide range, Alter- forms. Our results indicate that Agasicles hygro- nanthera sessilis is a slender-stemmed amphib- phila is the most primitive species of the genus ious amaranth that, in our limited study, shows and that the genus is centered in the lower basin of no noteworthy geographic variation. Therefore, if the Rio de la Plata. Forms extending more or less A. sessilis is indigenous to South America and if it is linearly in three different directions show progres- prehistorically tropicopolitan, it should serve to sively greater geographic and structural derivation show the miniscule amount of change (coevolution) (see Mayr 1970, p. 227). The trifúrcate configura- that has occurred in the host plant within those tion of the geographical distribution and the prin- areas where it interacts with Agasicles. There is no ciple of parsimony do not permit appHcation of evidence that the other amphibious amaranths have Darlington's rule of thumb (Darlington 1957; Nelson a prehistory of worldwide distribution. Therefore, 1969, 1974; Brundin 1972; Ball 1975). However, in they may not serve as indicators of coevolution. As view of the closely knit character of the Agasicles previously cited, Pedersen considers the affinities species and the probability of their relatively recent of A. sessilis to be with Southeast Asian species. evolution, we do not consider the applicability or nonapplicability of these rules as being important in Alternatively, since the primeval ecology of considering this problem at this stage in geological Alternanthera sessilis and Agasicles vittata is syl- time. Furthermore, as we have already noted (p. van in the very humid sub-Andean region, the ques- 120), in accordance with Amadon (1966), MacAr- tion arises. Could Agasicles have diverged from a thur (1972), and Haffer (1974), we consider that the terrestrial ancestral form that was a sylvan alticid geographically exclusive vittate species of Aga- in that region? There is also the possibility that the sicles constitute four semispecies of a superspe- three forms of fasciate Agasicles opaca could have cies. They evolved primarily on alligatorweed, evolved independently of their vittate congeners and they are indicated below within brackets. We through an ancestral form near a fasciate species of also list below the three unnamed geographically Phenrica (fig. 8). Neither of these alternative exclusive fasciate Agasicles forms that we consider evolutionary courses is borne out by the findings as being subspecific forms of A. opaca (Mayr 1970): of this study. Furthermore, the possibility that Agasicles underwent its radiation in a tropical re- Agasicles connexa gion such as the basin of the Amazon River is not interrogationis borne out by this study. However, in view of its lack vittata of winter diapause coupled with its irreversible, hygrophila autocidal, northward migrations documented in the Agasicles opaca lower Mississippi Valley Region (Vogt et al., cited Paraguay River form Plains of Mojos form in footnote 20), Agasicles hygrophila is an enigma Lower Amazon River form because we consider its lack of winter hardiness as an important indicator of tropical origins. On the other hand, considering that a form of summer 2^Lukefahr et al. (1964) point out that certain insect pests having winter diapause also have geographic ranges that do not diapause possibly exists in Agasicles hygrophila cross the Equator. They relate this to the inability of the in- (Vogt et al., cited in footnote 8) and considering that sects to enter diapause in areas between 10° north and 10° winter-diapausing flea beetles seek high ground. south latitude.

127 We may now recapitulate. The Recent South by the monophyletic groups resolved by phyloge- American disonychine flea beetles of the amphibi- netic Ccladistic') systematics." ous amaranths diverged from a terrestrial ancestral With respect to vicariance, we have endeavored form resembling Disonycha argentinensis and to explain that changing geographic factors resulted coevolved with the amphibious amaranths. The in the spHtting up of a wide-ranging ancestral form plants were advanced in their evolution when oí Agasicles hygrophila into the existing seven rec- Agasicles appeared. A trifúrcate distribution of ognized forms. Similarly we indicate the differen- forms resulted that centers on A. hygrophila. The tiation of three fasciate subspecific forms from the middle arm consists of polytypic fasciate A. opaca, less wide-ranging ancestral form of Agasicles which overlaps vittate A. hygrophila. The four vit- opaca. We feel our proposed phylogeny oí Agasicles tate semispecies that comprise the side arms are follows the important principles of phylogenetic geographically exclusive and constitute a super- systematics including Hennig's (1966) "rule of de- species. They have evolved primarily on alligator- viation" as discussed by Darlington (1970). We be- weed centered in the lower basin of the Rio de la heve our indulgence in considerations of dispersal Plata. After having undergone most of its evolution and center of origin are justifiably aprioristic in interacting with small-stemmed alligatorweed, fas- view of the relatively recent evolution of the exist- ciate pol3rtypic A. opaca diverged from the vittate ing insect forms under study and in view of our forms, continuing its evolution interacting with knowledge of their ecology. Furthermore, beyond mostly oversized stems of Alternanthera has- the scope of this bulletin, we are assembling infor- sleriana. Although this release from interaction mation (Vogt and Cordo 1976) on various interact- with small stems relates to an accelerated rate of ing systems of plants and insects in South America divergence from the vittate forms, it also relates to from a biogeographical standpoint. Much of this a slowed evolution of reproductive isolation and information constitutes "tracts of distributions" therefore speciation among the fasciate forms. that have influenced our biogeographical thinking From this summary, it becomes clear that the in this bulletin. taxon cycle of Agasicles is driven to a significant In this study, we have laid a foundation on which degree by the plant-stem and flea-beetle interac- more definitive studies can be made. We have tion. This is an important consideration because, as presented extensive documentation on the bioge- already discussed (p. 28), Ricklefs and Cox (1972) ography and phylogeny of a group of specialized have postulated that the progress of a species herbivores and their host plants that, in their in- through the taxon cycle results in "counterevo- teractions, provide an unusual opportunity for lution" and reduced competitive ability of that definitive studies. We have brought together ex- species. If this hypothesis is true, it may provide a tensive evidence for a probable center of origin of means of recognizing promising biocontrol agents, Agasicles in the form of Agasicles hygrophila and i.e., by its stage in the taxon cycle, or, in effect, by its ancestral forms. We relate evolution of the other its stage in speciation. three vittate species of Agasicles to three of Haf- We need to point out further that Nelson (1974) of fer's (1974) presumed forest refugia in tropical the emerging Croizat school of biogeographers South America during arid climatic periods of the rejects as ''aprioristic all 'clues' or 'rules' used to Pleistocene. We relate evolution of the more dis- resolve centers of origin and dispersal without ref- tinctive divergent group of three fasciate forms of erence to general patterns of vicariance^^ and sym- Agasicles to three regions of open insolated wet- patry (Croizat et al. 1974). With many others I lands to which their amphibious amaranth host is include as a rejectable apriorism Hennig's (1966) highly adapted. 'Progression Rule' (Ashlock 1974). Unencumbered We have not proved or disproved the suggested by aprioristic dispersal, historical biogeography is coevolution between host plant and specialized the discovery and interpretation, with reference to insect. We interpret our findings to mean that spe- causal geographic factors, of the vicariance shown ciation in Agasicles has been a process of geographical differentiation, with the rate of speciation seemingly controlled by the intensity of the host- ^^Vicarious species or forms, the subjects of vicariance, are important in biocontrol problems because they are ecological plant-stem and flea-beetle interaction. While this homologs, i.e., forms that are closely related phyletically and are interactive process may be considered to be co- essentially allopatric in distribution. They may be either semi- evolutionary, our findings indicate that the host species of superspecies or subspedfíc forms of polytypic species. plants were advanced in their evolution when A^a-

128 sides appeared and that the plants may not have and Spencer 1973). The performance of these in- changed appreciably as the flea beetles diverged sects in the biocontrol of alligatorweed during the and speciated. Our findings seem to be more in ac- past few years and in the years ahead will provide cord with the theory of sequential evolution pro- important information for testing the relation- posed by Jermy (1976). This theory emphasizes ship between the stages of the taxon cycle and the that ''the evolution of phytophagous insects fol- competitiveness of a biocontrol agent. Already lows the evolution of plants, the latter being one monotypic Vogtia malloi is showing superior sup- of the most important selection factors in the evo- pressive capability over alligatorweed under some lution of insects." conditions as compared with Agasicles hygrophila In the case of the possible coevolution of Al- (Spencer and Coulson 1976; Vogt et al., cited in ternanthera hassleriana and the three fasciate footnote 20). But monotypic Amynothrips ander- forms oí Agasicles, the oversized host-plant stem soni may be an enigma because it is showing only internodes do not necessarily preclude this possi- limited dispersal capability (Spencer and Coulson bility. In the case of the possible coevolution of 1976). In order that its natural dispersal capability alligatorweed and Agasicles hygrophila from their may be further determined, we urge that no further terrestrial ancestral forms, the evidence remains artificial dissemination be made of Amynothrips tenuous. But if the insect ancestral forms trans- beyond presently established colonies in Florida, ferred to the amphibious amaranths at a time Georgia, and South Carolina. Slow dispersal of this when the plants were in an advanced state of evo- insect in the United States may indicate absence of a lution, then the plants must have either increased in phoretic agent. growth and reproductive potential or developed Agasicles clearly has an old, if not ancient, at- phytochemical or subtle physical defenses or both, tachment to the amphibious amaranths that is because of coevolution associated with increasing obligatory. Its evolutionary history indicates con- specialization, and often increasing suppressive- tinuation of its confinement to aquatic habitats. ness, of the insects. We see little or no difference An insight into future evolutionary possibilities be- between this interactive process and that leading tween interacting alligatorweed and Agasicles hy- to ecological homeostasis that host-parasite systems grophila within the Southern United States may evolve toward as postulated by Pimentel (1963, be seen in this illustrated presentation of the evo- 1968). In phytophagous insects, the taxon cycle lutionary course that has taken place between the may be another manifestation of this same process amphibious amaranths and Agasicles in South combined with the effects of counterevolution- America outside the geographic range of A. hygro- ary processes occurring within the biotic com- phila. No deviations from amphibious amaranths munity (seep. 28). have occurred. Furthermore, in the Southern The piecing together of the probable evolutionary United States, no indigenous species of Alternan- history of this group of disonychine flea beetles and thera and no aquatic or amphibious species of their host plants affords various conclusions that plant has a stem structure that compares with alli- are of more direct importance in the biological con- gatorweed and might serve as a suitable alternative trol of weeds. Of general interest is the evidence for enclosure for pupating Agasicles hygrophila. and the conclusion reached on the center of origin As compared with less specialized Disonycha for Agasicles. This information suggests the impor- collata and D. xantho?nelas, Agasicles hygrophila tance of the lower basin of the Rio de la Plata as a and its congeners, with their many unusual spe- center of evolution for other amphibious and aquatic cializations, may be expected to have virtually no weeds such as Eichhornia, Pistia, and Sesbania potential for forming effective host-plant trans- and their associated insects. Also, from the stand- fers (disjunctions) in the Southern United States. point of biological control, the speciation that has We consider further the perfect transference of taken place in Agasicles provides an important the North American Disonycha collata and D. basis for comparison with two other important bi- xanthomelas and the imperfect orientation of D. otic agents of alligatorweed, viz., Amynothrips an- glabrata to terrestrial alligatorweed in the South- dersoni and Vogtia malloi. Neither of these two ern United States. Of these three North American unrelated monotypic genera has speciated in South Disonycha species, only Z). glabrata reaches south- America, and both insects have been successfully ern South America. This species, rather than D. introduced into the United States along with collata OTD. xanthomelas^ may be the species most Agasicles hygrophila (Maddox et al. 1971; Brown closely related toD. argentinensis intragenerically.

129 While less specialized Disonycha xanthomelas and tion foci as compared with the interior regions and D. collata are important suppressants of terres- their continental climates. Humid, cloudy, warm trial alligatorweed in the Southern United States seasons favor population increase as compared with (Quimby and Vogt 1974), they may not prove to be dry, sunny, hot seasons (Vogt et al., cited in foot- as suppressive or as suppressive pangeographically note 20). Interior regions of colder latitudes may as the more specialized D. argentinensis (pp. have both too brief a period of warm, cloudy, moist 23-24). weather in the late spring and autumn for popula- The divergence of Agasicles from Disonycha tion increase and too severe a winter for survival of probably occurred in the wetlands associated with Agasicles hygrophila^ which has no winter diapause the Paraguay River and the Paraná River, includ- (Maddox 1968; Vogt et al., cited in footnote 8). We ing the vast Chaco and Pantanal. Moreover, the doubt that this flea beetle will develop winter divergence may have required this vastness, this diapause capability or otherwise adapt itself climat- diversity of habitat, this geological history, because ically unless it is in the direction of improving its no comparable divergence in disonychines occurred orientation to favorable environments for overwin- in the much smaller area of wetlands in Mexico and tering or for growth and development. The demon- Central America, where Alternanthera obovata strated dispersal capability oí Agasicles hygrophila and possibly A. sessilis occur indigenously and from its permanent population foci near the Gulf of where an Alternanthera-oriented flea beetle quite Mexico is an important consideration for employ- comparable to Disonycha argentinensis exists in- ment of this insect on other continents (Vogt et al., digenously in the form of D. collata, cited in footnote 20). Considerations of introducing Agasicles hygrophila is the smallest species of its Agasicles into tropical regions, such as Southeast genus, and its normal host plant, alligatorweed, is Asia, should include the corresponding tropi- considerably larger in stem diameter than the cal species as well as the temperate to subtropical slender-stemmed aquatic amaranth Alternnnthera A. hygrophila. sessilis. Under normal conditions, pre pupal stem Considering Pimentel's (1963) recommendation entry by this flea beetle should not be hindered by for avoidance of host-parasite homeostasis in the host-plant stem diameter. However, under con- biocontrol agents and considering the stage II posi- ditions of heavy suppression by herbivores, regen- tion of the Paraguay River form of Agasicles opaca eration of alligatorweed of reduced stem diameters in the taxon cycle, this flea beetle may be useful to may constitute most of the surviving plants on some supplement A. hygrophila in suppressing al- sites. These reductions can be restrictive on suc- ligatorweed in the United States. Also, it may be cessful metamorphosis of Agasicles hygrophila, be- more tolerant of insolated conditions than A, hy- cause in nature, no species of Agasicles is known to grophila. However, for PimenteFs reconimenda- pupate outisde the host-plant stem internode. The tions to hold, the preferred biocontrol agent may small size of A. hygrophila may also simply be an necessarily have a geographic range exclusive of expression of the restrictive effects on its evolu- that of the target weed. tionary course of the reduced stem diameter cited With respect to the possible development of host above. This interaction may be affected by competi- resistance to Agasicles hygrophila, the normal el- tion with the Paraguay River form of Agasicles lipses and phenoclines may show the effect of the opaca in the rather broad zone of overlap in their interaction that, in time, results in marked ranges. Its small size may also be simply an expres- evolutionary change but survival of both members. sion of affinity with its closest extrageneric relative, This is most apparent in Alternanthera hassleriana Disonycha argentinensis, versus the three fasciate Agasicles forms. Amelio- Biogeographical, seasonal, and ecological find- ration of this interaction seems to have occurred, ings on Agasicles in South America are consistent resulting in greater prevalence of both plant and with findings in North America on the progress of insect members in insolated lagoons of the the introduced vittate Agasicles hygrophila (Mad- Paraguay and Amazon Basins. In contrast, the in- dox et al. 1971; Vogt et al., cited in footnote 20). The teraction between alligatorweed and Agasicles less insolated seasons of spring and autumn are hygrophila y which is probably the oldest involving more or less optimal for population increase. The Agasicles, still tends to be extirpative to the detri- ameliorated climate of coastal regions is also more ment of both the host plant and the dependent favorable for population increase; these regions insect. The other vittate species of Agasicles are usually include the only sites of permanent popula- similarly extirpative.

130 The genus Disonycha ranges throughout the tinensis may prove to be the ideal specialized sup- Western Hemisphere and is older geologically than pressant to reduce alligatorweed along the banks of Agasicles. D. argentinensis is somewhat apart drainage canals, bayous, lagoons, and ponds. This from its congeners, apparently in the direction flea beetle may show greater capability in following of Agasicles, with respect to certain characteris- rooted alligatorweed behind receding waters than tics of the adult (punctuation and form of head) and either D. xanthomelas or D. collata. Also, D. of the larva (some reduction in prominence of body argentinensis should be important in the Gulf of tubercles and setae). The pupa, however, shows Mexico region and in the Southeastern United no transitional features between Disonycha and States where D. xanthomelas does not occur (fig. Agasicles, Also, the adult D. argentinensis is very 37) and where D, collata alone usually makes less distinct from its suggested closest intrageneric rel- impact on alligatorweed than in the region where ative, Ö. ^Zaftra^a. both flea beetles occur in combination. In view of the terrestrial habits of D. argenti- There can be little doubt that Disonycha ar- nensis ^ there is probability that this insect is not gentinensis is a prime prospect for biocontrol of confined to the terrestrial growths of aquatic bankside alligatorweed in California, Australia, amaranths, because there is on land such greater and wherever else Alternanthera-oriented species diversity of both closely and distantly related of Disonycha do not indigenously occur. The plants. However, only three terrestrial plants are specialized host range of D. argentinensis should known as alternative hosts. All three are species of make it a safe introduction in those regions, Alternanthera, and it now seems unlikely that any whereas either Disonycha xanthomelas or D. alternative hosts exist outside this genus. None of collata could be destructive to various culti- the North American species oí Disonycha are con- vated crops. fined to plants of the genus Alternanthera except Of special interest is our proposal that introduc- possibly Z). eximia of the Caribbean region. None tion of one ecological homolog to compete with are so specialized in the direction of alligatorweed as another for weed control may create the situation isD. argentinensis of South America. known as character displacement or ecological shift. The more specialized host spectrum of Disonycha This situation may cause division of the shared argentinensis indicates that it may be a more effec- host-plant spectrum of the two homologs. The re- tive biocontrol agent against terrestrial alligator- sulting reduction in number of host plants available weed than are the less specialized North American to each homolog would constitute a process of species,!), xanthomelas SindD.'collata (pp. 23-24). specialization. Therefore, if more specialized phy- There is a need to determine the relative virulence tophages are more efficient suppressants, the pro- or suppressive index for each of these three flea cess could lead to improved suppression, possibly beetles in its interaction with alligatorweed. This on the part of both insects. Besides division of should be done for both standardized and given host-plant spectrum, character displacement, or simulated (special) climatic conditions. Assuming ecological shift, may occur in other ways that result that the more specialized D. argentinensis is the in increased specialization: by division of the ecolog- more suppressive insect, it would have the potential ical range of the shared host plants; by division to displace both D. collata and D. xanthomelas on between the homologs of the anatomy of the shared alligatorweed, but it would have little or no effect host plants; and by the development of distinct on either North American flea beetle on their periodicity on the part of the insects. If character non-Altemanthera hosts. This problem involves displacement does not occur, one of the homologs ecological nonanalogs and is discussed further in may be displaced geographically, or it may become Vogt and Cordo (1976). Also, assuming that the extinct. Geographical displacement may be ex- mimetic predator-ectoparasites L^^èia viridipennis, pected to progress gradually but perceptibly within of Disonycha collata^ and Lebia analis, of D. a few years. It would be associated with the de- xanthomelas, are sufficiently host specific not to velopment of character displacement which could be attack D. argentinensis, the South American flea a very slow process. However, character displace- beetle should have an added advantage. It would be ment must be included in any careful consideration freed of its specific mimetic predator-ectoparasites, that is made of ecological homologs for possible in- Lebia securigera (mimetic) and L. concinna (non- troduction to control weeds. mimetic) (Vogt and Cordo, cited in footnote 15). From the grand experimental standpoint, intro- With these apparent features, Disonycha argen- duction of Disonycha argentinensis into the South-

131 ern United States might show to what degree the We close with consideration of still another view hypothesis holds that the more specialized herbi- expressed by Huffaker et al. (1971): "Theoretically, vore is the more efficient host suppressant. From general predators tend to serve as regulators of another angle, such an introduction might show a community stability while specialists tend to regu- relationship between degree of specialization of late single species stability. . . . There is no sharp herbivore (consumer species) to environmental line; the two are interrelated. ..." With this view stability or homeostasis. It might help us to under- in mind it seems clear to consider the gypsy moth, stand why some specialized agents such as many Lymantria dispar, as an exotic organism and as a leaf miners are only lightly suppressive. Is it simply general predator that is capable of regulating com- because of parasite-predator pressure? In this con- munity stability in the Eastern North American nection, but seemingly inconsistent while being forest formation. Presumably, this insect can be seemingly cogent, are the recently proposed rating considered to have similar but reduced capability in criteria for biotic agents in which Harris (1973) its indigenous range in the Old World. Also, we may downgrades specialization while emphasizing how consider without semantic difficulties that both vitally the insect's attack affects the plant. Yet specializedA^asicZes hygrophila dnidVogtia malloi Frick (1974) judiciously points out that there are are capable of regulating alligatorweed, both in its two criteria of primary importance in choosing can- indigenous ranges in South America and in the didate insects for biocontrol: "(1) a narrow range of Southern United States. host plants, none of which can be crop plants [a This field-oriented systematic study of a biocon- manifestation of specialization] and (2) an attack by trol agent and related species together with their the plant feeding stages (larvae, nymphs, adults) of host plants is intended to complement laboratory growing tissues vital to the plant rather than tissues studies employed in the screening of biocontrol of little importance to plant growth such as senes- cent foliage or pith." The shift by phytophages from agents. The field-oriented systematic approach af- more vital host tissues to those that are less so is an fords contextual perspective not usually or readily obvious evolutionary course leading to homeostasis, obtainable in laboratory screening studies. Much and it seems to have occurred in some specialized of the type of information that field-oriented sys- leaf miners that have shifted in orientation from tematic studies are based upon is stored in bio- young leaves to older leaves. However, we recog- logical collections, but both field studies and the nize no comparable shift having occurred in any of biological literature are necessary for development the Disonycha oriented to Alternanthera. of the context.

132 LITERATURE CITED

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135 APPENDIX

Analytical Data for Measured Flea Beetle and Amphibious Amaranth Characters

Table A-1.—Composition of measured samples of host plants

Number Suppressant Alternanthera species of stems Locality Agasicles and growth habit measured species A. philoxeroides; regeneration of Agasicles- 12 Banks of Reconquista River near Cas te- A. hygrophila. suppressed plants; leaves of each stem infested lar, Buenos Aires Province, Argentina. with larvae. Fig. 48, eUipse D (n = 12). A. philoxeroides; at margin of incipient mat, float- 1 Laguna Espejo near Santa Fe, Sante Fe Do. ing, possibly approaching a form with a cordlike Province, Argentina. attachment. Figs. 47 and 48, point E. A. philoxeroides; usually competing among erect 17 Deltaic marshland at head of the Guaiba Do. stems; collected within the known range of the River, Ilha do Paváo, Rio Grande do Sul vittate species of Agasicles. Fig. 47, ellipse C State, Brazil. {n=88) and fig. 48, ellipse C (n=92).'' Do 3 Roadside pools near San Miguel del Monte, Do. Buenos Aires Province, Argentina. Do 7 Deltaic swamp. Brazo Largo near Yaraví, Do. Entre Ríos Province, Argentina. Do 3 Deltaic marshland, Rio de las Palmas near Do. Campana, Buenos Aires Province, Argentina. Do 1 Laguna Espejo near Santa Fe, Santa Fe Do. Province, Argentina. Do 5 Arroya Riachuelo near Corrientes, Cor- Do. rientes Province, Argentina. Do 2 Ituzaingó, Corrientes Province, Argentina Do. Do 1 Itá-Ibaté, Corrientes Province, Argentina Do. Do 2 Streetside ditches, Posadas, Misiones Pro- Do. vince, Argentina. Do 2 Shallow cove of Paraná River at Posadas, Do. Misiones Province, Argentina. Do 4 Drying lagoons along Paraguay River oppo- Do. site Asunción, Paraguay. Do 2 Delta (?) of Itajai River at Itajai, Santa A. connexa. Catarina State, Brazil. Do 4 Praia Braba, just south of Cabeçudas, Santa Do. Catarina State, Brazil. Do 25 Paranaguá, Paraná State, Brazil Do. Do 11 Dique district, Salvador, Bahia State, A. interrogationis. Brazil. Do 4 Vermelho River near Salvador, Bahia Do. State, Brazil. Do 7 Salvador, Bahia State, Brazil Do. See footnotes at end of table.

136 Table A-1.—Composition of measured samples of host plants—Continued

Alternanthera species 'l"'"^^'' Suppressant and growth habit °^^*«"^, ^"^^^^ Agasicles measured species A. philoxeroides; usually competing among erect 11 Banks of Amazon River at Leticia, Ama- A. vittata. stems; collected within the known range of the zonas, Colombia, vit täte species of Agasicles. Fig. 47, ellipse C (n=88) and fig. 48, ellipse C (n=92). i—Continued Do 23 Iquitos, Loreto Department, Peru Do. A. sessilis; competing among erect stems. Figs. 14 Huallaga River near Tulomayo, Huánuco Do. 47 and 48, ellipse F in=28). Department, Peru. Do 4 Streetside ditch, Pucallpa, Loreto Depart- Do. ment, Peru. Do 9 Banks Amazon River at Leticia, Amazonas, Do. Colombia. A. hassleriana; free floating but with cordlike 10 Ilha Careira, Amazon River, Amazonas A. opaca. attachment. Figs. 47 and 48, ellipse B (n = lS). State, Brazil. Do 3 Lago Branco, Monte Alegre, Para State, Do. Brazil. A. hassleriana; competing among large Eich- 3 Drying lagoons along Paraguay River Do. hornia at edge of dry lagoon (the normaDy float- opposite Asunción, Paraguay, ing plants from the dry lagoons are unsuitable for measurement). Figs. 47 and 48, points A.

^An inadvertent mismatch of samples of measured specimens is represented by ?i=88 and n=92. ^Accessioned specimens of U.S. National Herbarium.

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138 Table A^.—Composition of measured samples of flea beetles

Number Alternanthera Unused Flea beetle measured Locality host-plant preserved species specimens Disonycha argentinensis 6 Fallow dry fields near Reconquista River and Cas te- A. philoxeroides .. 41 lar, Buenos Aires Province, Argentina.

Agasicles hygrophila (n=45 $, 0 Vila Nova, Rio Grande do Sul State, Brazil do 0 42(?). Do 4 Ilha do Paváo, Rio Grande do Sul State, Brazil do 0 Do 16 16 Montevideo, Uruguay do 102 Do 3 3 San Miguel del Monte, Buenos Aires Province, Ar- do 0 gentina. Do 3 0 Yaraví, Entre Ríos Province, Argentina do 1 Do 3 4 Río de las Palmas near Campana, Buenos Aires Prov- do 14 ince, Argentina. Do 13 14 Reconquista River near Cas telar and Las Barrancas, do 205 Buenos Aires Province, Argentina. Do 3 1 Santa Fe, Santa Fe Province, Argentina do 0 Do 1 0 Arroya Riachuelo near Corrientes, Corrientes Prov- do 1 ince, Argentina.

Agasicles connexavnexa 5 10 Itajaí, Santa Catarina State, Brazil do

Agasicles interrogationis 5 9 Dique district, Salvador, Bahia State, Brazil do (n=18$,18(î). Do 13 9 Cachoeira River near Itabuna, Bahia State, Bra- do zil.

Agasicles vittata (n = 14$, 1 O Huallaga River near Tingo María, Peru A. sessilis 2SS). Do 0 15 Huallaga River near Tulomayo, Peru . do Do 13 8 Amazon River near Leticia, Colombia A. philoxeroides and A. sessilis.

Agasicles opaca, Paraguay 2 1 Shallow, pristine lagoons along Riachuelo Antiquera A. hassleriana .. and Amazon River forms above Puerto Antiquera, Chaco Province, Argen- combined (n =31 $, 28 ^ ). tina. Do 10 11 Turbid lagoons, disturbed by cattle, near Barran- A. hassleriana and queras, Chaco Province, Argentina. A. philoxeroides. Do 1 1 Seasonally dry lagoons along Paraguay River oppo- do site Asunción, Paraguay. Do 12 12 Lago Careira, clear-water lagoon of Amazon flood A. hassleriana y plain below Manaus, Amazonas State, Brazil. A. philoxeroides, and A. sessilis. Do 3 Clear, pristine "varzea" lagoon of Amazon flood A. hassleriana plain near Monte Alegre, Para State, Brazil.

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140 Table A-5.—Means, standard deviations (SD), and coefficients of correlation (r) for the two pairs of characters measured in three Alternanthera species [Millimeters]

Correlated Alternanthera Alternanthera Alternanthera Alternanthera characters 1 sessilis hassleriana philoxeroides philoxeroides in =28) in = m in=S8) regeneration X y (n = 12)

Ascdng L Int'n W3: Mean .. . . X 197.25 18.307 326.4 — y 1.6714 5.523 4.489 — SD ...... X 84.61 9.499 179.28 — y .4822 2.4235 1.9842 — r .7172 .9415 .01534 Int'n L Int'n Wl: Mean .. . . X 35.32 47.54 51.77 43.75 y 1.4036 14.75 3.450 1.933 SD ...... X 8.577 7.590 17.66 17.499 y .2516 3.875 1.202 3.114 r .3581 .2058 .1707 .5422

^Character abbreviations are identified in table 3.

Table A-6.—Means, standard deviations (SD), and coefficients of correlation (r) for the 11 pairs of characters measured in females of the 6 flea beetle species [Millimeters]

Correlated Disonycha Agasicles Agasicles Agasicles Agasicles Agasicles characters argentinensis hygrophila connexa vittata opaca interrogationis^ X y (^=6) (w=45) (n=5) (n = U) (n=31)

PrW PrL: Mean ....x 1.5834 1.2146 1.3291 1.2995 1.3284 1.8282 y .8112 .9276 1.0577 1.0178 1.0109 1.3421 SD X .0422 .0671 .0710 .0541 .0522 .0887 y .0197 .0504 .0356 .0337 .0386 .0744 r 5615 .8297 .8964 .6907 .7959 .6243 EL EW: Mean ....x 3.9233 3.8533 4.0700 4.4072 4.3886 5.3290 y 2.5383 2.2702 2.4780 2.4261 2.4143 3.4184 SD X .0852 .2444 .2225 .1537 .1747 .2735 y .0376 .1644 .1158 .0979 .1299 .2472 r 7251 .6851 .8507 .6625 .8898 .5619 BL BTh: Mean x 5.4167 5.4109 5.7800 6.3833 6.2429 7.5968 y i:6950 1.6958 1.8000 1.7933 1.8400 2.4113 SD X .1169 .4568 .2387 .2618 .1785 .5199 y .0394 .1245 .0612 .0827 .1295 .1243 r 6735 .7204 .9405 .6545 .8352 .5911 HW HL: Mean .... x 1.0389 .9441 1.0083 .9613 .9621 1.1804 y .5096 .4536 .4867 .4437 .4829 .5973 SD X .0273 .0411 .0206 .0245 .0287 .0525 y .0426 .0341 .0171 . .0279 .0342 .0449 r 4857 .5699 -.3176 -.0581 .5611 .1857 See footnotes at end of table.

141 Table A-6.—Means, standard deviations (SD), and coefficients of correlation (r) for the 11 pairs of characters measured in females of the 6 flea beetle species—Continued [Millimeters]

Correlated Disonycha Agasicles Agasides Agasicles Agasicles characters argentinensis hygrophila connexa vittata opaca ^ y in=6) (n=45) (^ = 5) interrogatix)nü^ (n = U) (n=31) low lAW: Mean....x .2397 .2068 .2129 .1963 .2001 .2716 y .0847 .0677 .0568 .0647 .0718 .0944 SD X .0117 .0100 .0053 .0075 .0077 .0126 y .0070 .0046 .0024 .0050 .0051 .0062 r 9092 .4128 .6988 .3057 .5220 .5808 U2W UIW: Mean ....x > .3562 .3596 .6259 .7448 .5837 1.0678 y .4732 .4618 .2952 .2378 .2458 .3306 SD X .0428 .0816 .0403 .0490 .0336 .0930 y .0780 .0833 .0679 .0542 .0435 .1017 r -.8866 -.3415 .2947 -.4279 -.2531 -.3395 AL MTL: Mean ....x 2.6450 2.5860 2.7700 3,1328 3.1779 3.3852 y 1.2064 1.1252 1.2199 1.3676 1.3583 1.5323 SD x .0464 .1428 .1483 .1419 .1057 .2052 y .0470 .0677 .0473 .0579 .0881 .1029 r 5157 .7910 .8502 .5046 .7345 .6586 4AL 3AL: Mean .,..x . 1037 .1120 .1093 .1334 .1375 .1517 y .0922 .0736 .0825 .0894 .0923 .1050 SD X .0065 .0094 .0149 .0094 .0091 .0122 y .0055 .0079 .0130 .0075 .0072 .0084 r -.0672 .5231 -.1724 .5220 .4826 .5004 6AL 5AL: Mean ....x .0937 .0963 .1017 .1216 .1205 .1314 y .0807 .0900 .0957 .1141 .1081 .1219 SD X .0031 .0074 .0042 .0058 .007a .0119 y .0050 .0064 .0060 .0051 .0076 .0079 r 4629 .5812 .7071 .3949 .8398 .6207 7AL 7AW: Mean .,..x .0877 .0944 .1041 .1088 .1081 .1345 y .0592 .0551 .0592 .0520 .0565 .0840 SD X .0072 .0069 .0033 .0036 .0079 .0116 y .0010 .0046 .0Q71 .0034 .0049 .0096 r 1974 .6634 -.3059 .4849 -.1688 .5875 PYW PYL: Mean ....x .7800 .8033 .8611 .8958 .9101 1.0482 y .2600 .2718 .2683 .6130 .5215 .4932 SD X .0261 .0508 .0131 .0328 .3423 .0554 y .0189 .0541 .0171 .0570 .0697 .0694 r -.6908 .2698 -.8729 -.0546 ,1847 .0555 ^Character abbreviations are identified in table 4. The measurements are illustrated in fig. 46. % = 18 except for the PYW.PYL correlation, where n=17.

142 Table A-7.—Means, standard deviations (SD), and coefficients of correlation (r) for the 11 pairs of characters measured in males of the 6 flea beetle species [Millimeters]

Correlated Disonycha Agasicles Agasicles Agasicles Agasicles Agasicles characters argentinensis hygrophila cofinexa interrogationis vittata opaca X y (^=6) (n=42) (ri = 10) (n = 18) (n=23) {n=2S)

PrW PrL: Mean....a^ 1.435 1.107 1.222 1.187 1.208 1.699 y '805 .8588 .955 .949 .955 1.289 SD X .0843 .0635 .0545 .0548 .0500 .0868 y -0434 .0621 .0464 .0338 .0382 .0930 ^ 9506 .6598 .8541 .7390 .8614 .8202 EL EW: Mean ....x 3.580 3.440 3.540 4.054 4.0500 4.982 y 2.180 1.941 2.085 2.133 2.1621 3.020 SD X .2445 .1730 .4326 .2922 .2505 .4137 y .1195 .1192 .1029 .1129 .1064 .2145 ^ 9312 .8359 .8514 .5566 .8646 .8101 BL BTh: Mean ....x 4.977 4.831 5.040 5.444 5.487 6.736 y 1-483 1.456 1.545 1.612 1.643 2.182 SD :x .3871 .2781 .3026 .1977 .3152 .4388 y .0880 .0731 .1165 .1229 .0806 .1588 ^ 9460 .7247 .9043 .3720 .8014 .6676 HW HL: Mean....x .9558 .8861 4.054 .911 .915 1.123 y Mil .4141 2.133 .4378 .4415 .5583 SD X .0549 .0317 .2922 .0224 .0303 .0523 y .0464 .0251 .1129 .0468 .0327 .0460 ^ 9692 .5111 .5566 .2395 .2807 .5152 low JAW: Mean....x .2113 .1892 .1904 .1770 .1872 .2614 y .0757 .0603 .0518 .0571 .0624 .0861 SD X .0145 ,0085 .0087 .0093 .0080 .0160 y .0106 .0059 .0030 .0053 .0059 .0065 ^ 9126 .6220 .6507 .3282 .3131 .7336 U2W UIW: Mean ....x .3406 .2960 .5713 .662 .5209 .977 y .4472 .4517 .2761 .2349 .2225 .2997 SD X .0553 .0628 .0587 .0555 .0409 .0697 y .0824 .0902 .0706 .0542 .0377 .0610 ^ 0392 -.7231 -.6291 -.6475 -.0097 -.0311 AL MTL: Mean....x 2.628 2.535 2.768 3.047 3.179 3.666 y 1.164 1.042 1.0811 1.247 1.266 1.553 SD X . 1207 .1544 .1847 .1088 .1287 .2681 y .0482 .0626 .0560 .0667 .0814 .1000 ^ 9826 .6834 .9471 .4887 .8030 .6894 4 AL 3AL: Mean.... a; .0997 .1013 .1076 .1252 ,1339 .1643 y .0907 .0695 .0759 .0858 .0915 .1108 SD X .0082 .0090 .0097 .0077 .0107 .0133 y .0070 .0072 .0076 .0050 .0064 .0080 ^ 7Ö30 .5200 .7153 .6464 .2722 .5312 6AL 5AL: Mean.... a? .0952 .0941 .1047 .1194 .1223 .1412 y .0842 .0889 .0951 .1095 .1089 .1249 SD X .0064 .0083 .0069 .0067 ,0070 .0107 y .0061 .0060 .0072 .0072 .0098 .0102 See footnotes at end of table.

143 Table A-7.-Means, standard deviations (SD), and coefficients of correlation (r) for the 11 pairs of characters measured in males of the 6 flea beetle species—Continued [Millimeters]

Correlated Disonycha Agasiclts Agasicles Agasicles Agasicles Agasicles characters^ argentinensis hygrophila connexa interrogationis vittata opaca y. y (n=6) (n=42) (n = 10) (n = 18) (n=23) (n=28)

6AL 5 AL—Continued: r 8788 .7357 .5425 .5868 .5576 .5833 7AL 7AW: Mean x .0867 .0921 .1029 .1055 .1126 .1390 y .0548 .0514 .0572 .0504 .0537 .0857 SD X .0076 .0055 .0072 .0057 .0086 .0126 y .0024 .0037 .0028 .0029 .0031 .0072 r 1936 .5436 .3984 .2907 0.2230 .2968 PyW PyL: Mean ....x .7056 .7354 .7441 .7982 .886 1.019 y .2886 .2525 .2387 .2470 .3412 .3649 SD X .0484 .0410 .0368 .0309 .0497 .0475 y .0237 .0471 .0541 .0398 .0543 .0788 r 1149 .1375 .5286 -.0992 .2479 -.0398 ^Character abbreviations are identified in table 4. The measurements are illustrated in fig. 46.

Table A-8.—Means, standard deviations (SD), and coefficients of correlation (r) for the measurements of pronotal width (PrW) and length (PrL) of the combined vittate Agas/c/^s species^ [Millimeters]

Correlated characters Females Males PrW (x) and (n=82) (n=93) PrL (2/) Mean x 1.2596 1.1601 y .9696 .9103 SD X .0796 .0753 y .0647 .0686 r .8738 .8338 ^Agasicles hygrophila, A. connexa, A. interrogationis, and A. vittata.

144 Table A-9.—Composition of measured samples of Agasicles opaca supplemented in 1975 and divided into three geographic forms

Number Altemanthera Unused Flea beetle measured Locality host-plant preserved species specimens

Paraguay River form (n =379, 1 Shallow, pristine lagoons along Riachuelo Antiquera A. hassleriana 0 37cî).i above Puerto Antiquera. Doi 10 10 Shallow, clear lagoons below Puerto Antiquera do Do^ 10 11 Turbid lagoons, disturbed by cattle, near Barran- A. hassleriana and queras. A. philoxeroides. Do2 2 Ditches with high biochemical oxygen demands, east side, A. philoxeroides .. Formosa, Formosa Province, Argentina (terra firma). Do2 1 Dry lagoons along Paraguay River opposite A. hassleriana and Asunción, Paraguay. A. philoxeroides. Do2 0 Disturbed pond near Luque, Paraguay (terra firma) A. philoxeroides .. Do2 0 Shallow backwater of Lago Ypacaraí west of Luque, Para- ...... do guay (terra firma). Do2 6 Shallow, turbid roadside ponds near Paraguay River and A. hassleriana 0 north of Asunción, Paraguay (terra firma). Do2 6 Backwaters along Paraguay River at Corumbá, A. hassleriana and 0 Mato Grosso State, Brazil. A. philoxeroides.

Plains of Mojos form (n= 15 15 Shallow ponds scattered over Plains of Mojos east of A. hassleriana 11 159, Ida). Trinidad, Beni Department, Bolivia.

Lower Amazon River form 12 12 Lago Careira, clear-water lagoon of the Amazon flood A. hassleriana, 0 (n = 18 9,15 (Í ). plain, below Manaus, Amazonas State, Brazil. A. philoxeroides, and A. sessilis. Do 3 Clear, pristine "varzea" lagoon of the Amazon flood plain A. hassleriana 0 near Monte Alegre, Para State, Brazil.

^Below confluence of Paraguay and Paraná Rivers, Chaco Province, Argentina. ^Above confluence of Paraguay and Paraná Rivers.

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147 Specific Names Referred to in Text, With Authors

Agasicles: Beta vulgaris L. Lebia— connexa (Boheman) Chenopodium album L. Continued: hygrophila Selman and Vogt Coleom£gilla quadrifasciata Schönh. securigera Chaudoir interrogationis (Clark) Disonycha: viridipennis Dejean opaca Bechyné argentinensis Jacoby Ludwigia peploides (H. B. K.) Raven vittata Jacoby bicarinata Boheman Lymantria dispar (L.) Agromyza altemantherae Spencer camposi Barber Lysathia: Alternanthera: collata(F.) flavipes (Boheman) ficoidea (L.) R. Br. conjugata (F.) ludoviciana (Fall) halimifolia (Lam.) Standl. conjuncta Germ. Melanagromyza: ex Pittier eximia Harold altemantherae Spencer hassleriana Chod. glabrataiY.) marellii (Brethes) kurzii Schinz ex Pedersen lim,bicollis (Le Conte) Musca domestica L. marítima (Mart.) St. Hil. pennsylvanica (lUiger) Oenothera biennis L. obovata (M. and G.) Killip polittda Horn Ophiomyia sp. poss. buscki (Frost) paronychioides St. Hilaire procera Casey Phaedon (Paraphaedon) philoxeroides (Mart.)Griseb. prolixa Harold tumidulus Germar pungens H. B. K. recticollis Jacoby Philoxerus: reineckii Briq. triangularis (Say) portulacoides St. Hil. repe?^s (L.)Steud. uniguttata (Say) vermicularis (L.) R. Br. sessilis (L.) R. Br. xanthomelas (Dalman) Phoenicia sericata Meigen tetram^ra Fries Drosophila melanogaster Meig. Pyrrhalta (Galerucella) Altica: Erynephala maritimst (Le Conte) nymphaeae (L.) foliácea LeConte Herpetogramma bipunctalis (F.) Sagra femorata (Drury) litigata Fall Iresine diffusa H. and B. Spinada olerácea L. marevagans Horn Lebia: Stellaria media (L.) Cyrillo Amynothrips andersoni O'Neill analis Dejean Trianthema portulacastrum L. Anolis chrysolepis Duméril and Bibron concinna Brullé Vogtia malloi Pastrana

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