Aliso: A Journal of Systematic and Evolutionary Botany Volume 21 | Issue 1 Article 5 2002 New Species of Phoradendron (Viscaceae) from Mexico and Guatemala and a Synopsis of Species in Section Pauciflorae Delbert Wiens University of Utah; Rocky Mountain Forest and Range Experiment Station Frank Hawksworth Follow this and additional works at: http://scholarship.claremont.edu/aliso Part of the Botany Commons Recommended Citation Wiens, Delbert and Hawksworth, Frank (2002) "New Species of Phoradendron (Viscaceae) from Mexico and Guatemala and a Synopsis of Species in Section Pauciflorae," Aliso: A Journal of Systematic and Evolutionary Botany: Vol. 21: Iss. 1, Article 5. Available at: http://scholarship.claremont.edu/aliso/vol21/iss1/5 Aliso, 21(I), pp. 33-43 :0 2002, by The Rancho Santa Ana Botanic Garden, Claremont . CA 9171 1-3157 NEW SPECIES OF PHORADENDRON (VISCACEAE) FROM MEXICO AND GUATEMALA AND A SYNOPSIS OF SPECIES IN SECTION PAUCIFLORAE 2 DELBERT WIENS I AND FRANK HAWKSWORTH 'D epartment of Biology University of Utan Salt Lake City, Utah 84JJ2 and Rocky Mountain Forest and Range Exp eriment Station Ft. Collins, Colorado 80526-8121 2dece ased A BSTRACT As presently interpreted Phoradendron sec tion Pau cifiorae consists of 15 spec ies. These mistletoes parasitize primarily conifers. We describe seven new species. make sta tus changes for four species, and provide information on the hosts and di str ibution of all members of the sec tion. New species described are: Phoradendron abietinurn Wiens, on Abies durangen sis in Chihuahua, Durango, and Jalisco, Mexico; P. acuminatum Wiens, on Cupress us lusitanica in Gu atem ala; P. flavomarginatum Wiens, on Juniperus fiaccida in Nuevo Leon , Mexico; P. lta wksworthii Wiens. on Juniperus in New Mexico, west Texas, and Coahuila, Mexico; P. olivae Wiens, on Cupressus lusitanica in Colima and Jalisco, Mexico; P. rufescens Wiens, on Juniperus spp . in San Lui s Potosf, Mexi co ; and P. sedifo lium Wiens on Cupressus /usitanica in Chiapas, and Hidalgo. Mexico. Three taxa previ ousl y recognized as subspecies are raised to specific rank: P. densum Torr. ex Trel., P. paucifi orum Torr., and P. /ibocedri (Engelm.) Howell. Also P. saltillense Trel. , which had been placed in synonymy und er P. botleanum subsp. densum, is accorded species status, In addition, three new epiparasit ic speci es of Ph oradendron are described. Epiparastic mistletoes are known to para sit ize only other species of mistletoes- in this instance Phoradendron or Cladocolea (Loranthaceae). Key words: epiparasitism, new species, para sitic plants, Phoradendron . Viscaceae . INTRODUCTION actio n to the numerous species named by Trelease (1916); however, the classification of taxa as subspe­ Since the publication of the acataphyllous species of cies that are widely distributed over thousands of ki­ Phoradendron (Wiens 1964), considerable additional lometers seems inappropriate for subspecific recogni­ information has accumulated regarding sect. Pauciflo­ tion . We suspect that additional research will demar­ rae. This is primarily the result of our extensive field cate the existence of geographically definable elements studies in Mexico and Guatemala over the course of (subspecies) within some of the wide ranging species, approximately 26 years. All the taxa discussed here e.g., the populations of P. densum occurring in central have been studied in the field and the critical, defining Arizona on Cupressus, and perhaps various population characteristics of the new species were evaluated at the systems of the widespread P. saltillense in northern population level. In addition to reporting new species, Mexico. several taxa previously recognized as subspecies in 1964 are elevated to species status and one species, MATERIALS AND METHODS Phoradendron saltillense Trel., previously synony­ mized under P. bolleanum (Wiens 1964), is also ac­ The morphological differences most useful in the corded species status. There are no subspecies pres­ construction of keys for separating the species, often ently recognized among these species. We include a leaf size, are notoriously variable characters. Nonethe­ synopsis of the species currently included in section less, leaf size tends to fall out statistically, as well as Pauciflorae (Table I), and a key to the species. internode length, since the latter is generally a corre­ The earlier taxonomic conservatism of Wiens late of overall plant size. Characters, such as stature (1964), who gave subspecific recognition to a number and size, are not especially useful for con structing of taxa now regarded as species, was partially a re- keys , but are still important features in defining the species, along with host differences. The specifics of these quantitative features are described in Wiens I Present address: White Mountain Research Sial ion. 3000 East Line Street, Bishop. California 93514, and Rancho Santa Ana Bo­ (1964), or in the descriptions of the new species pre­ tanic Garden, 1500 North College Avenue, Claremont, California sented herein. The problem is well illu strated by the 91711. relationship between P. juniperinum and P. libocedri. 34 Wien s and Hawksworth ALISO Table I. Synop sis of Phoradend ron Section Pau ciftorae, Taxon Hosts Distribution J. P. abietinum Wien s sp. nov . Abies duran gensis Chihuahua to Jalisco. Mexico 2. P. acum inatum Wiens sp. nov. Cupressus lu sitanica Guatemala 3. P. bolleanum (Se ern.) Eichl. Juniperu s. Arbutus Chihuahu a to Jali sco, Mexico 4 . P. ca p itellatum Torr. ex Trel. Juniperus Southwestern U.S.A; northwestern Mexico 5. P. densum Torr. ex Trel. Juniperus , Cupressus Southwestern U.S. A.; northern Baja Ca lifornia, Me xico 6. P. flavomar gin atum Wiens sp. nov. Juniperus flaccida Nuev o Leon , Mexico 7. P. hawksworthii Wiens sp. nov . Juniperus New Mexico, Texas, U.S.A; Coahuila, Mexico 8.P. [uniperinum Engel. Juniperus. Cupressus Southwestern U.S.A; north ern Mexico 9. P. libocedri (Enge lrn.) Ho well Calocedrus decurrens Southern Oregon , California, U.S .A.; Baja Cali- forn ia Non e. Mexic o 10. P. minutifolium Urban Juniperus North ern and central Mexico II. P. olivae Wiens sp. nov. Cupressu s lusitanica Co lima, Jalisco, Mexico 12. P. pauciflorum Torr. Abies concotor Southwestern U.S.A; Baja Ca lifornia, Mexico 13. P. rufes cens Wien s sp. nov. Juniperu s San Lui s Potosi, Mexico 14 . P. saltillen se Trel. Juniperus. Cupressus Northeastern and eastern Mexico 15. P. sedifolium Wiens sp. no v. Cupressu s Chiapas, Hidalgo , Mexico The latter species has internodes that are significantly mm ). The leaves are likewise either comparatively longer than those of P. juniperinum, and long inter­ sm all (mostly < 25 X 8 mm) or redu ced to scales. The nodes are correlated with the distinctive pendulous length of the inflorescence, the number of fertile in­ habit. Yet neither morphology nor molecular data ternodes produced, and the number of flowers per fer­ (Ashworth 2000) identify clear-cut interspecifi c differ­ tile internode are also relatively small in comparison ences. with species in other sections. Th e staminate inflores­ In addition to the description of new species in sect. cences are usually < 10 mm long with mostly 1-2 (3) Pauciflorae, we also include descriptions of three new fertile internodes, with each fertil e internode common­ species of epiparasitic spe cie s of Phoradendron, i.e., ly bearing < 20 flowers. The pistillate inflorescences mistletoes that are known to parasitize only other mis­ typically have I (2) fertile internodes, and consistently tletoes. In this instance the host mistletoes are either produce only two flowers per fert ile internode; two other species of Phoradendron or Cladocolea (Lor­ pistillate flowers per fert ile internode is the best single anthaceae). The subject of epiparasitism is a fascinat­ morphological feature defining sect. Pauciflorae. In ing phenomenon deserving of further study. More de­ addition to the morphological and host affinities that tailed information on the subject is available in Wiens characterize the group, Ashworth (2000) showed that and Calvin (19 87), and in Polhill and Wien s (1998). molecular data also confirm the uniformity of the Unfortunately, Kuijt (pers. cornrn., 1996) has indi­ group, as well as its monophyletic origin. cated that there are potential nomenclatural difficulties with the maintenance of the name Pau cifiorae as a CHANGES IN TAXONOMICST ATUS section of Phoradendron sen su Wiens (1964). This is­ sue will not be addressed here , as there is no question Specimens are cited only for tho se species for which of the species involved or the cohesiveness of the we have significant new distributional data. For distri­ group, regardless of what name is ultimately attached butional information of other spe cies, see Wien s to it. (1964). RESULTS AND DI SCUSSION Phoradendron densum Torrey ex Trelease. Genus Phoradendron, 27, 1916. (= P. bolleanum (Seem. ) The species of section Pau ciflorae (Wiens 1964) Eichler subsp. dens um (Torr.) Wien s, Brittonia 16: parasitize primarily Juniperus, Cupressus, and to a 29, 1964 ). lesser extent, Abies. Members of the group are typi­ cally reduced in terms of thei r overall size, as well as Phoradendron densum, as here defined, occurs on their floral and vegetative features, when compared to Juniperus and Cupressus and has a distribution rang­ most other members of Phoradendron. Overall the ing from southern Oregon (Jackson Co.) throughout species are rarely over 0.5 m high (exceptions are P. California to the Sierra San Pedro Martfr, Baja Cali­ acuminatum and P. olivae, which may be over 1 m). forni a Norte, Mexico. There are interesting outlying Reduced overall size is typically correlated with short­ populations in ce ntral Ari zona on Cupressus (Cocon­ ened internode lengths and widths (mostly < 25 X 4 ino , Yavapai, Maricopa, and Gil a Counties), that de - VOLUME 21, NUMBER 1 New Species of Phoradendron 35 serve further study as possible subspecies. The known is associated with infected Abies concolor (Hawk­ elevational range is 200-2300 m. sworth and Wiens 1966).