A nuclear perspective on endemism in northern flying squirrels (Glaucomys sabrinus) of the Alexander Archipelago, Alaska

We used microsatellites to examine population structure and genetic diversity in northern flying squirrels in the Alexander Archipelago of Southeast Alaska, with an emphasis on the endemic Prince of Wales flying squirrel (Glaucomys sabrinus griseifrons). Previous work showed this subspecific designation coincided with a distinct mitochondrial lineage on eleven islands (the Prince of Wales [POW] complex). To obtain a nuclear perspective on this lineage and to further investigate genetic diversity among insular populations, we examined six microsatellite loci in 233 flying squirrels representing eight populations in Southeast Alaska and a population from interior Alaska (seven island and two mainland localities). Island populations have lower heterozygosity and allelic diversity than mainland populations. Overall, population pairs show a pattern of isolation by distance, indicating there is little long-distance gene flow across the archipelago. Analyses of microsatellite allele frequencies reveal significant differences between the POW complex populations and others we examined, a finding congruent with the mitochondrial data. The population from Mitkof Island, a non-POW complex island, also differs significantly from other populations in allele frequencies. The six POW complex populations are genetically very similar, suggesting current or recent gene flow among these islands, while there seems to be no gene flow between the POW complex and other populations in Southeast Alaska. Our data corroborate mitochondrial DNA results indicating that G. s. griseifrons is genetically distinct and suggest a general pattern of isolation of insular flying squirrels in Southeast Alaska.