Great Basin Naturalist Memoirs

Volume 6 The Bark and Ambrosia of North and Central America (Coleoptera: Article 7 Scolytidae), a Taxonomic Monograph

1-1-1982

Biogeography

Stephen L. Wood Monte L. Bean Life Science Museum and Department of Zoology, Brigham Young University, Provo, Utah 84602

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Recommended Citation Wood, Stephen L. (1982) "Biogeography," Great Basin Naturalist Memoirs: Vol. 6 , Article 7. Available at: https://scholarsarchive.byu.edu/gbnm/vol6/iss1/7

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have diverged further than the other groups theories are essentially correct: (1) the biolog-

from the original ancestral line. The ical species concept (Mayr 1963) is valid, (2) Phloeotribini also diverged rather early as biological speciation occurs through a pro- evidenced bv the protibia of Aricerus and by cess of geographical isolation, during which the very different, sublaniellate, antennal time isolated populations of a parent species club. The Hypoborini and Polygraphini ap- differentiate and become reproductively iso- pear to be specializations that diverged lated from one another (Mayr 1963), and (3) a rather recently from the Phloeosinini. process of continental drift has occurred that ScoLYTiNAE.— The basic stnictural rela- has had an effect on the geographical distri- tionship of most Scolytinae to Platypodidae is bution of groups (Wegener 1924). It is closer than to Hvlesininae, although the bio- also necessary to eliminate from this dis-

logical affinity is closer to most Hylesininae. cussion those species and genera that are The strongly procurved antennal sutures of known to have been introduced to or export- Coptonotus (and the obscure lines that sug- ed from North and Central America through gest obsolete sutures in other Coptonotinae modern human commerce (Wood 1977).

and a few Platypodinae) is a common charac- Most notable in this regard are the imported ter in Scolytinae (Scolytini, Ctenophorini, genera , Hijpocnjphalus, and Micracini, Xyloctonini), but occurs only in Premnobius, and the exportation of Gnatho- Diamerini {Diamerus) and Bothrosternini {Pa- trichits materiariiis (Fitch) to France and Mi- giocerus, Eupagiocerus) in the Hylesininae. croborus boops Blandford to Africa. The Scolytini apparently diverged very early An analysis of the tribal groups of Scoly- from the main evolutionary line in Scoly- tidae reveals the following relationships (Ta- bles Cactopinini are found only in tinae, as evidenced by antennal, tibial, meta- 1, 2). The Both- pleural, and other characters. The divergence southwestern North America. The are restricted to of Scolytoplatypodini and Ctenophorini soon rosternini and Ctenophorini the tropics of North and South America; followed, as evidenced by a significant Scolytini (except Scolytus extends to Eurasia) change in tibial characters, and these geo- and Corthylini (except Pityophthorus extends graphical replacements then diverged from to Eurasia; there are also a few aberrant Afri- one another. The remaining Scolytinae re- can forms) are almost exclusively American. place unsocketed lateral tibial spines with Phloeotribini are largely American, with a socketed teeth that apparently were derived few species of in Eurasia, except from setae. Except for the socketed tibial that the monotypic Aricerus appears to have teeth, Carphodicticini most nearly resembles reached Australia very early in the formation my concept of a primitive platypodid in an- of the group. The Polygraphini, Crypturgini, tennal, frontal, pronotal, coxal, metapleural, and Xyloterini are of obvious Eurasian origin metatergal, and abdominal characters. How- and reached northern North America rather ever, the tibiae, and other characters, place it recently. The Hylastini, Hylesinini (except more nearly intermediate between Pro- Phloeoborus that was derived biogeographi- toplatypus and Dryocoetini. The Cryptur- cally from South America), and Ipini (except gini, Dryocoetini, Ipini, Xyloterini, and Xy- Acanthotomicus, which probably reached leborini represent a unit of closely related South America from Africa in pre-Tertiary tribes. Micracini and Cactopinini appear time) are also of Eurasian origin, but the in- related, as do Xyloctonini and somewhat volvement appears much older and more Cryphalini. relationship of Corthylini to The complex. The Phrixosomini, Hypoborini, and other tribes is not clear; they exhibit some Micracini apparently reached North and very primitive features as well as many of the Central America rather recently from South most specialized ones in the family. America, but exhibit a strong, much earlier relationship to the African fauna. The Tomi- BIOGEOGRAPHY cini, Phloeosinini, Dryocoetini, Xyleborini, and Cryphalini are diverse and indicate more Extraterritorial Affinities complex endemic origins and inter- relationships with other areas. The Hyorr- To establish a basis for this discussion, it is hynchini, Diamerini, Scolytoplatypodini, assumed that the following hypotheses and 1982 Introduction 45

Carphodicticini, and Xyloctonini do not oc- North America, and in Pityogenes only three cur in North America, although two of three of several groups reached North America. genera of Carphodicticini occur in South Comparable multiple migrations appear to America and Diamerini (Old World) appears have affected several other groups with equal to replace geographically Bothrosternini, and magnitude when faunal transfers were suffi- Scolytoplatypodini (Old World) replaces ciently early to permit secondary radiations. Ctenophorini. In some instances the migrations were so re- The principle original centers of adaptive cent that speciation of the populations on dif- radiation in the family appear to be North ferent continental land masses may not yet be America for Hylastini, , and Cac- complete. topinini; South America for Phrixosomini (and Africa), Bothrosternini, Phloeotribini, Table 3. A comparison of the number of genera of Scolytidae in North and Scolytini, Ctenophorini, Micracini (and Af- Central America, listed by tribes, to the world fauna. rica), and Corthylini; Eurasia for Hylesinini (and Africa, except South America for Phloeoborus), Phloeosinini (and Africa), Ipini (and Africa), Xyloterini, and Cryphalini (and Africa); Africa for Hypoborini, Polygraphini, Crypturgini, and Dryocoetini. The radiation of Xyleborini has progressed explosively from

the Tropics, but the pattern is not yet clear. Secondary radiations of each tribal group may also occur in newly occupied areas. For example, the Ipini apparently originated in tropical Africa as the precursors of Acan- thotomicus then spread northward into Eu- rasia, giving rise to a new stock. The portion of the new stock that remained in Eurasia ap- parently gave rise to Orthotomicus and Pi- tyogenes, and the portion that reached North America gave rise to Ips and Pityokteines. Later, elements of Orthotomicus and Pitijo- genes reached North America and elements of Ips and Pityokteines reached (or returned to) Eurasia to give rise to the present faunas. This is based on the fact that, of nine species groups of Ips in North America, six are shared with Eurasia; no unique group occurs in Eurasia. Similarly, in Pityokteines only one of three groups reached Eurasia, in Orthoto- micus only one of several groups reached 46 Great Basin Naturalist Memoirs No. 6

Table 4 continued.

Alaska and Central Total species Canada USA Mexico America in fauna

Hylesinini Hijlastin us 1 Phloeoborus

Tomicini Hyhirgopinus Demlroctonus 1982 Introduction 47

Table 4 continued.

Alaska and Central Total species Canada USA Mexico America in fauna Micracini

Fsi'tiilothysanoes 1 Stcnorleptus Thijsanoes rhlot'odeptus Micracis Micracisella Hiflociiriis 48 Great Basin Naturalist Memoirs No. 6

Table 4 continued.

Alaska and Central Canada USA Mexico

Corthylini Styplilosoina DendroteruH 2 7 Arapttis I 25 Connphthocramilus Spen)HypIitliorus rseudopityophthorus 12 14 Pityuborus 2 5 Pityotrkhus 2 Gnathuleptiis Conoplithoriis 4 10 4 Pityophthorus 41 99 102 Dacnophthorus 1 Gnathotrichus 3 7 11 Gnatliotrupes Tricolus 6 Amphicranus 9 Glochinocerus 1 Mefacortbyhts Monorthrum 2 5 22 Microcorthylus 4 Cortliycyclon 1 Corthylocurus 4 Corthyhis 1 4 17

Total 179 477 605 1982 Introduction 49

Both Dohirgus and Xyloterinus are mon- otypic and endemic to North America, but they were undoubtedly derived from a Eura- sian source in that no potential ancestor or near relative exists in the Western Hemi- sphere. Nine genera are much more diverse in North America, and all Eurasian species groups in these genera are represented in

America; consequently, it is concluded that all Eurasian species in these genera were de- rived directly or indirectly from North Amer- ica. These genera include:

Hijlurgops 50 Great Basin Naturalist Memoirs No. 6

record nor has it invaded Eurasia until very andersoni Swaine is common recently (D. annandi may be an exception). in interglacial lake deposits in Ontario (Mor- In addition, 11 of the existing 20 tribes of gan, pers. comm.), but presently does not oc- North American Scolytidae are represented cur south or east of the Northwest Terri- in the fossil record by modern genera. Seven tories. Similarly, C. carri Swaine was of the nine tribes not represented are of trop- common in postglacial deposits in western ical distribution in or were probably too rare New York; this species presently is known temperate North America for one to expect from Manitoba and New Brunswick, but not fossilization. from the intervening area. Because the apparent connection between The present land bridge connecting North southern South America and southern Africa and South America has facilitated a faunal was broken by continental drift no later than exchange between these areas. South Ameri- early Tertiary (most geologists place it 15-30 ca was an island during much of the Tertiary, million years earlier), I had presumed that but was connected to North America at the the availability of such a route for migration beginning and again at the end of that period would not be reflected in the living scolytid (Darlington 1965). During the Pleistocene fauna. Tliis is not the case. The above fossil this land bridge formed and broke several record lists 12 modern genera that are 30 times. In those periods when the land bridge million or more years old in five different was broken, a series of islands persisted and tribes. Furthermore, it is noted that, among preserved much of the fauna that had mi- groups now restricted basically to the Ameri- grated to them while the connection was can tropics and Africa, the genera Phrixo- complete. Many of these species had either soma, Cladoctonus, Micracis, Acanthoto- migrated along mountain chains or adapted micus, certain Hypothenemus, and certain to the higher elevations on the islands, where Xyleborus groups, the paired but different they either preserved migrating populations genera in the Phloeosinini, Hypoborini, or were modified through selection into new Micracini, and in the Dendrocranulus group geographical races or distinct species. The of genera of Dryocoetini, the paired but dif- groups most conspicuously restricted to high ferent tribal groups Bothrosternini and Dia- merini, and the Ctenophorini and Scolytopla- altitudes and affected by the "island" effect are the tropical typodini suggest that such a connection did Xylechinus, Gyinnochilus, Chrarnesus, Stegomertis, Dendroterus, exist and that the basic patterns of scolytid Pseu- dopityophthorus, the xylomycetophagous phylogeny were established long before that Corthylini, land connection was severed. and some . The island ef- fect also have halted the southward mi- Based partly on the above dates and diver- may gration of the conifers, and all scolytids uti- sity, one might speculate that the Scolytidae lizing as hosts, in northwestern originated in conjunction with the origin of them Nicaragua. The speciation that resulted from coniferous gymnosperms perhaps as early as the island effect combined with the later mi- the Triassic, when conifers were a dominant gration of the Bothrosternini (except some plant group. In fact. Walker (1938) named Cnesinus), , Phrixosoma, Phloeo- Paleoscohjtus and Paleoipidiis from holes and borus, Phloeotribus, most Scolytini (except engravings in petrified Arancariuxylon wood some Scolytus), most Ctenopherini, from the Triassic (Chinle formation) of Ari- many Hypothenemus, and Xyleborus in the lowland zona. Whether or not these were made bv areas produced a rich faima that appears un- scolytids or their ancestors is open to question. equaled elsewhere in the world in an area of similar size. Considerably more collecting and studv must precede a detailed analysis of American Biogeography the scolytid biogeography of this area. The most distinctive faunal area in North Pleistocene glaciation affected the distribu- America appears to be the desert plateau re- tion of Scolytidae in northern North America gion from southern California, southern Ari- by causing extinction in some areas and pro- zona, and southwestern New Mexico to the viding refugia in others. For example. Isthmus of Tehuantepec. A considerable 1982 Introduction 51 amount of endemism is evident here in the infest those pines and extend into Mexico are Micracini, Cactopinini, Dendroteriis, Pityoph- another example of this faunal connection. thonis, and, perhaps, in several other phloeo- Southern Florida is distinctive and appears phagous Corthyhni. Superimposed upon this to be more nearly like Cuba or other Antilles desert plateau are those species that breed in Islands than like the southeastern United conifers in the mountains that traverse the States in its scolytid fauna. A majority of the area and those that penetrate the moist low- species appear to have reached the area re- land pockets of tropical forest on the margins cently by crossing over water naturally (flota- of the desert region. tion, wind, etc.) or through commerce. A

Because 39 percent of all North and Cen- high percentage of the imported species are first detected in in tral American Scolytidae are known only North America southern Florida. from their type series, and because most of The scolytid fauna of the northern con- these species are from Mexico to Nicaragua, iferous forest is distinctive. For the most part, a useful analysis of the biogeography of this it is rather monotonous but exhibits some en- area is not possible at the present time. demism due to apparent refugia of past gla- In view of the faunal exchange that has cial periods in Alaska and Nova Scotia. Ele- taken place between North America and ments of this fauna extend southward along Asia, both geologically recent and ancient, it the mountains of the eastern and western appears significant that only two species of United States. have reached Eurasia, and one The Pacific Coast belt from Alaska to of those in comparatively recent times. The southern California contains a rich fauna high concentration of species and diversity in with many endemic species particularly in Mexico suggests a Mexican origin of Den- , Carphoboriis, Ainiphagus, and droctonus, with a comparatively recent in- Scohjtus. From this area many species appear vasion of north temperate areas. This possi- to have migrated since the last period of gla- bility is supported by the fact that no ciation into the mountains of Idaho, Wyom- endemic Ips species, which share the same ing, Utah, Colorado, New Mexico, and north- hosts with Dendroctonus, have developed in ern Arizona. Others, namely some Mexico. All Mexican Ips have distributions Phloeosinus, Pseudopityophthorus agrifoliae extending into the United States. Only four of Blackman, and Monarthrwn dentigerum (Le- 16 American species of Dendroctonus pres- Conte) have spread into Arizona at a time ently do not occur in the Mexican plateau when the level of precipitation was higher area, and all four are of recent origin (one of than at present. these is in Guatemala). Pityoborus, Gnatho- trichus, Conophthorus, and several Pityoph- Origin of Tribes thorus exhibited similar patterns of distribu- tion; for the most part, all breed in Pinus. In view of the above summary of data re- The southeastern deciduous forest forms a lating to the biogeography of American distinctive faunal area. evidenced pres- As by Scolytidae, perhaps some speculation as to ent relict refugia the on eastern margins of the origin of major groups in the world fauna the Mexican plateau, this area formerly ex- within the family is in order. This is based on tended southwestward into Mexico. Several the assumption that (1) a geologically recent Thysanoes, Cnesinus strigicollis LeConte, and Bering connection existed between Alaska

Micracis swainei Blackman have present dis- and Siberia on more than one occasion, (2) tributions that follow this pattern. A few Africa and South America were connected or forms that apparently originated in this area, at least were close enough to permit migra-

such as Micracisella nanuki (LeConte), M. tion by flight until the early Tertiary, and (3) opacithorax, and M. hondurensis Wood, have South America was an island during most of been modified by speciation. If the pines of the Tertiary, but was connected to North the southeastern United States are considered America near the beginning and near the end to be part of the deciduous forest, Dendroc- of that period and at one or more subsequent tonus frontalis Zimmermann and the Ips that times. 52 Great Basin Naturalist Memoirs No. 6

Phrixosomini, Hypoborini, Micracini, Den- Polygraphini, Xyloterini, and Crypturgini drocranulus (Dryocoetini), Acanthotomicus probably originated in this area after the sep- (Ipini), and parts of Xyleborini and Crypha- aration of Africa and South America, or at lini evidently originated in the African-South least dispersal into South America did not oc-

American land mass before separation. cur if there was a connection. The dispersal Phrixoscmia was probably then a relict genus of Hylesinini, Tomicini, and Hypoborini, and rigidly adapted to the Guttiferae and has re- many Dryocoetini, Xyleborini, and Crypha- mained virtually unchanged in both areas lini is too complex to permit speculation as to since the separation. Micracini had diver- origin. sified and the basic structure of most genera The representation of Hylesinini in North was almost fixed, as evidenced by paired or America is largely restricted to Hylesinus identical genera in both areas; diversification and Ainipliagus; both genera occur in adja- of the American segment of this group has cent Asia and are obvious rather recent addi- been more extensive since the separation. tions to the North American fauna. Hylesi- Ctenophorini apparently also had a pre- nini is represented in Central and South separation origin, but the African segment America only by Phloeoborus, which is of an- became modified into modern Scolvtopla- cient origin and may be allied to the African typodini largely through the adoption of the Dactylipalpus. Hylastinus was introduced ambrosial habit and then dispersed as far as through commerce from Europe within the Japan and Australia. The Diamerini-Both- past century. rosternini may have had a preseparation ori- Most of the Tomicini are restricted to hosts gin, but both diverged and diversified. in the Pinaceae; consequently, their phyletic

Phloeotribini, Scolytini, and Corthylini ap- history is closely linked to that group. Excep- pear to have a postseparation South Ameri- tions include Xylecliinns (part) (almost world- can origin; all appear to have spread into wide), Hylurgopiniis (North American), and North America at the beginning of the Ter- Dendrotrupes (New Zealand). This appears to tiary and from there into Eurasia after the be a declining group that has undergone at

Tertiary. An early representative of least two radiations and is difficult to Phloeotribini reached Australia, apparently interpret. from southern South America, possibly either Except for Phloeosinus, the Phloeosinini by island hopping or flotation, resulting in consist of the essentially Neotropical Carpho- the monotypic Aricertis. At a much later date toreiis, Dendrosiniis, , and Pseii- Phloeotribus invaded North America and dochmmesus, the Ethiopian Chilodcndron, from there it reached Eurasia. The occur- Hylesinopsis, and Trypograpfms, with Clodoc- rence of Pityophthorus (including aberrant al- tonus occupying both Ethiopian and Neo- lied forms) in Africa may indicate a slightly tropical areas, the Oriental Phloeocranus, and earlier origin for Corthylini; this group prob- the Australian Hyleops. Little relationship is ably reached North America by early Ter- seen in the group of genera from one conti- tiary and Eurasia by late Tertiary. Phloeosi- nent when compared to the group from an- nini may also have originated in the African- other continent. Phloeosinus, however, ap- South American area but subsequent dis- pears to be of south Asian origin and to have persion has obscured the pattern. invaded Eurasia, North America, and Austra- Because of repeated and recent con- lia perhaps as early as the early Tertiary. nections to adjacent areas, the role of North Except for the almost pantropical Acon-

America in the origin of tribal groups is un- thotomkus, it appears that Ipini originated certain, although it has played a significant (from Acanthotomicus?) in southern Eurasia role in the formation of generic groups with- or Africa. The early stock invaded North in several tribes. A possible North American America from the north, where Pityokteines origin of Hylastini in the remote past is sug- and Ips formed while Pityogenes and Orthoto- gested but not clear. tiiicus formed in Eurasia. One or more recent The role of Eurasia, the Indian subcon- connections between the land masses enabled tinent, and Africa (in addition to that elements of each of these four genera to in- mentioned above) is also unclear. The vade the territory of the other. In each case 1982 Introduction 53 the invaded area contains only a minor frac- These included the National Museum of Nat- tion of the species-groups, all of which are ural History (Smithsonian Institution), Ameri- found in the area of origin (see also Extra- can Museum of Natural History, Museum of territorial Affinities, above). Comparative Zoology, Illinois Natural His- The Dryocoetini consist of several ele- tory Survey Collection, Ohio State University ments, most of which are of south Asian ori- Collection, State University of New York, gin. Exceptions include Dryocoetes (sensu Syracuse, Oregon State University, University strictu) and Lymantor, which invaded north- of California at Berkeley, Colorado State em North America recently, and Dendrocra- University, California Academy of Sciences, nuliis, which recently invaded southern the USDA Forest Service Collections (at Cor- North America from South America, and vallis, Oregon; Berkeley, California; Albu- Thamnurgus, Xylocleptes, Triotemnus, and querque, New Mexico; and Fort Collins, Col- possibly Tiarophorus of Eurasia and Africa. orado), Canadian National Collection of The origin of these latter groups evidently at Ottawa, British Museum (Natural predates the separation of Africa and South History) at London, Museum National America sufficiently that ancestral Den- d'Histoire Naturelle at Paris, Universitates drocranulus, which is almost congeneric with Zoologiska Museum at Helsinki, Zoological Xylocleptes, could disperse into South Institute of the USSR at Moscow, Forest Re- America. search Institute at Dehra Dun (India), and The Cryphalini appear to have subdivided the Karl E. Schedl Collection at Lienz, Aus- early into the Cryphahis group of genera that tria. Type and other material was sent by radiated out from southern Asia and reached mail for my examination from numerous in- northern North America rather recently and stitutions and private individuals. Because the Hypothenemiis group of genera that radi- many of these asked to remain anonymous, ated out from the African-South American none are mentioned here. In all, more than land mass. A large number of genera and spe- 187,000 North and Central American speci- cies are involved and cannot be adequately mens were examined during the course of the analyzed without a thorough taxonomic study. study. (2) Measurements of the length of speci- mens depart from the usual method in that METHODS the head was not included for any species (other workers have included the head for Several departures from normal procedure Hylesininae and Scolytini). In general, mea- were followed in this study. Those relating to surements of the body, pronotum, and elytra the examination of specimens include: (1) were made from a position perpendicular to

Early in this study it was learned that the the dorsal (discal) surface at a position near published records of distribution and host the middle of the object being measured. could not be relied upon as being authentic. (3) All proportions were standardized; that

Consequently, virtually every record cited in is, the width was always divided into the this work was based upon my personal exam- length of the body, pronotum, or elytra ination of voucher specimens and types. Ex- (others have divided the shorter into the ceptions are clearly indicated. Almost all ex- longer measurement regardless of the result). isting primary types, including the types of (4) Insofar as practical, the descriptions genera, have been examined by me and com- were standardized to make comparisons eas- pared directly in detail to material from the ier and to avoid the illusion of describing dif- same or a nearby locality. All type com- ferences when, in fact, none exist. parisons are cited. Due to misidentification, (5) Distributions are presented just in a numerous published distribution and host re- brief summary that outlines the most dis- cords are not cited because they do not per- tantly separated limits of range. This is then tain to the species mentioned in the liter- followed by a listing of political subdivisions ature. Numerous collections were visited from north to south beginning with Alaska during the course of this study to obtain data (listed as though it were a separate country, and to examine type and other material. due to its geographical position) to Panama.