Glacial vicariance and historical biogeography of rock ptarmigan (Lagopus mutus) in the Bering region

In this paper, we address alternative hypotheses for the evolution of subsp ecies of rock ptarmigan (Lagopus mutus) endemic to the Aleutian Archipelago . To do this we examined patterns of genetic differentiation among populati ons of rock ptarmigan in the Aleutian Islands and parts of both Alaska and Siberia. Variation in mitochondrial control region sequences of 105 rock pt armigan from 10 subspecies within the Bering region revealed three major ph ylogenetic lineages, two of which are endemic to the Aleutian Islands. Acco rdingly, haplotype and nucleotide diversities of rock ptarmigan within the archipelago are much higher than within mainland Alaska or Siberia. For Ale utian rock ptarmigan, analyses of molecular variance indicated significant genetic structuring and low estimates of gene flow among populations, despi te small interisland distances within the archipelago. However; isolation b y distance did not describe the pattern of gene flow or differentiation at this scale. Our estimates of divergence times of lineages suggest that Aleu tian rock ptarmigan became isolated prior to the most recent Pleistocene gl aciation event (late Wisconsin Stade) and that current patterns of genetic variation reflect the postglacial redistribution of divergent lineages and subsequent limited gene flow In addition, genetic divergence among lineages was concordant with the distribution of plumage types among subspecies. Th e patterns of genetic variation described here for rock ptarmigan provide e vidence for the role of glacial vicariance in contributing to genetic diver sity within this and other Bering region species.