Biogeography of tundra voles (Microtus oeconomus) of Beringia and the southern coast of Alaska

Abstract

Allozymic, chromosomal, and morphologic variation among six subspecies of Microtus oeconomus was examined and related to the biogeographic history of Beringia with a particular focus on the Prince William Sound region. Chromosomal and allozymic similarities between Alaskan and Russian M. oeconomus corroborate previous hypotheses of a relatively recent 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 Montague Island in Prince William Sound, M. o. operarius from the Copper River Delta, and M. o. yakutatensis from the Doame River Delta. M. o. macfarlani from interior Alaska exhibited higher allozymic variation, indicating a larger effective population size and longer history than populations from the southern coast of Alaska. Allozymic evidence of gene flow between M. o. macfarlani and M. o. operarius from the Copper River Delta suggested that the southern coast of Alaska was colonized from interior Alaska since the last glacial advance. The larger body size of M. o. elymocetes from Montague Island suggested that this population may have an older age structure compared to other populations.