BIOGEOGRAPHY OF TUNDRA VOLES (MICROTUS-OECONOMUS) OF BERINGIA AND THESOUTHERN COAST OF ALASKA

Allozymic, chromosomal, and morphologic variation among six subspecies of Microtus oeconomus was examined and related to the biogeographic h istory of Beringia with a particular focus on the Prince William Sound region. Chromosomal and allozymic similarities between Alaskan and Ru ssian M. oeconomus corroborate previous hypotheses of a relatively rec ent invasion across the Bering Land Bridge from Russia, In populations from the southern coast of Alaska, unique alleles were detected in M. o. operarius from Hinchinbrook Island and M. o. elymocetes from Monta gue Island in Prince William Sound, M. o. operarius from the Copper Ri ver Delta, and M. o. yakutatensis from the Doame River Delta. M. o. ma cfarlani from interior Alaska exhibited higher allozymic variation, in dicating a larger effective population size and longer history than po pulations from the southern coast of Alaska. Allozymic evidence of gen e flow between M. o. macfarlani and M. o. operarius from the Copper Ri ver Delta suggested that the southern coast of Alaska was colonized fr om interior Alaska since the last glacial advance. The larger body siz e of M. o. elymocetes from Montague Island suggested that this populat ion may have an older age structure compared to other populations.