| Summary: | Thesis (M.S.) University of Alaska Fairbanks, 1995 Phylogeographic patterns of genetic and morphologic variation were explored among six subspecies of the Holarctic tundra vole (Microtus oeconomus). but focused on those populations occurring in southcoastal Alaska. Allozyme electrophoresis and karyotyping revealed that, although levels of intraspecific variation were low compared to other species of Microtus. allozymic divergence was concordant with regional glacial history. Tundra voles from interior Alaska became established prior to the last glacial retreat. However, populations from southcoastal Alaska were founded more recently. Tundra voles from Montague Island, an endemic subspecies, exhibited features of the island syndrome (i. e., gigantism, older age structure). Factors potentially responsible for insular gigantism were assessed. The findings of this study fail to support the hypothesis that the island syndrome is a direct result of interspecific competition. Other density-dependent factors, such as predation, may be responsible for body size and demographic changes in these insular rodents. U.S.D.A. Forest Service, Chugach National Forest and U.S. Fish and Wildlife Service, Ecological Services
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