Great Basin Naturalist Memoirs Volume 6 The Bark and Ambrosia Beetles 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 Follow this and additional works at: https://scholarsarchive.byu.edu/gbnm 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 This Chapter is brought to you for free and open access by the Western North American Naturalist Publications at BYU ScholarsArchive. It has been accepted for inclusion in Great Basin Naturalist Memoirs by an authorized editor of BYU ScholarsArchive. For more information, please contact [email protected], [email protected]. 44 Great Basin Naturalist Memoirs No. 6 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 animal 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 Hylastinus, 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 Phloeotribus 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, Tomicini, 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 Hylesinus Alniphagus Phloeoborus Tomicini Xylechinus Pseudohylesinus 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 Carphoborus 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-