The islands, 800-1000 km W of the coast of Ecuador, have been available for terrestial colonization for about 3 million years. At least 54 families, 214 genera and 366 species are present. Comparatively few families (10) contain endemic genera (13) that may represent early colonizations. Species flocks occur in usually flightless members of 7 genera. Adaptive radiation is evident in 3 genera of tenebrionids. The species are 24% native (having naturally dispersed from C or S America), 67% being endemic to ≥1 islands, and 9% have been introduced by man. Virtually nothing is known of the bionomics of the species. The fauna of 335 native and endemic species is estimated to have originated from at least 257 successful ancestral colonizations. Over 3 million years this is an average rate of one successful colonization every 11 700 yr, and 1.4 new species per ancestral colonization. Most of the colonists reached the islands either through the air as "aerial plankton' (60%) or by rafting on oceanic flotsam (39%) from C or S America. Extinctions were more prevalent in "glacial-arid' periods, and colonizations more prevalent in "interglacial-humid' periods. Rate of species introduction has increased with human visitation and colonization. Factors suppressing species proliferation in Galapagos beetles, compared with those in other insular areas, seem to be as follows, in probable order of importance: lack of strong ecological diversity, proximity to mainland areas, proximity of main islands to each other, geological youth, and recent development of a more suitable (wetter) climate. An appendix presents new beetle records for the islands. -from Authors

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Journal Canadian Journal of Zoology
Peck, S, & Kukalova-Peck, J. (J.). (1990). Origin and biogeography of the beetles (Coleoptera) of the Galapagos Archipelago, Ecuador. Canadian Journal of Zoology, 68(8), 1617–1638. doi:10.1139/z90-242