Phyletic, biogeographic, and ecologic relationships among relictual montane populations of least chipmunks (Eutamias minimus) from Arizona, Colorado, and New Mexico were examined by analysis of pelage color, cranial and bacular morphology, protein electrophoresis, and habitat characteristics. Unlike previous investigations of geographic variation involving these populations, a pattern of relationship and differentiation corresponding to contemporary geographic discontinuities in the Southwest is demonstrated. Populations along the east and west sides of the Rio Grande Valley constitute distinct evolutionary lineages, with the most geographically isolated populations exhibiting the greatest amount of genetic divergence. This pattern of differentiation is consistent with the hypothesis that montane corridors present during the Pleistocene facilitated colonization by ancestral northern stocks in accordance with vicariant biogeographic theory. Microhabitat assessments demonstrate that least chipmunks inhabit a diverse spectrum of environmental regimes ranging in elevation from 2,400 to 3,900 m, and encompassing several habitat types. These results are consistent with observations on other populations of this species, yet contradict the hypothesis that least chipmunks in the Southwest have such restrictive ecologic requirements as to be predisposed to rapid extinction during interglacial episodes of the Pleistocene. The significance of this study to the most recent vicariant explanation of southwestern montane mammal biogeography is discussed.
引证/输出
预览资料
文章 : 英语