The phylogeography and post-glacial expansion of the boreal chickadee (Poecile hudsonicus)

Abstract

Using a combination of both mitochondrial DNA and microsatellites, as well as spatio-geographic modelling, this study examines how the most recent glaciations may have affected the population genetic structure of the boreal chickadee (Poecile hudsonicus), a small resident passerine of the North American boreal forests. The mtDNA data support a separation between eastern and western populations, with central populations containing a mixture of haplotypes from both the east and west. Estimated dates place the divergence during the Wisconsin (56.2-129.7 kya). Microsatellite analyses support the separation of Newfoundland from all mainland populations, indicating that the eastern straits are restricting gene flow. No evidence for reduced gene flow was found for the Rocky Mountains. The results suggest the use of multiple glacial refugia, one in Beringia and one in the east, followed by stepping-stone colonisation and secondary admixture.