Biogeography and insularity of small mammals on Great Basin mountain ranges.

摘要

This study examines the distributions of small mammals on Great Basin mountain ranges. The theory of island biogeography has been applied to a variety of "insular" terrestrial environments, among them the Great Basin. Previous studies interpreted the relationship of number of small mammal species to montane area to indicate Pleistocene colonization, post-Pleistocene habitat fragmentation, and differential extinctions controlled by montane area. Fourteen small mammal species on Great Basin mountains composed a homogeneous "boreal" suite, with the Great Basin mountains analogous to islands, and no significant small mammal colonizations since the Pleistocene.; The results of this research shows that the small mammals on Great Basin mountain ranges do not form a logical suite of boreal species. The insularity or isolation of species on montane habitats appears to be a function of ecological specialization and ability to exploit low-elevation habitats. Habitat generalists are found on more mountain ranges and utilize low-elevation habitats. In contrast, habitat specialist species are found on fewer ranges, yet several specialist species persist on small- to medium-sized mountain ranges. Area was shown to be a less effective predictor of species number than previously reported.; The faunal dynamics of Great Basin mountain ranges suggest that they do not function as islands in the sense of an equilibrium of species, since colonization is probably nonexistent for some species, yet may be common for others. Post-Pleistocene extinctions have occurred in several species, concentrated in the more southerly mountain ranges. These southern mountains' latitudes and lower basin floor elevations probably effectively isolate most of the resident mammal species that utilize high-elevation habitats. In contrast, higher-latitude ranges are more commonly connected by riparian corridors, basin floor elevations are frequently at higher elevations, and woodland and shrub vegetation may form dispersal corridors between these ranges.; Island biogeographic theory appears to be too general to be used with any great accuracy in describing or predicting Great Basin montane mammal faunas. Local environmental conditions appear to be more important than area in determining the numbers and composition of species.