Comparative phylogeography of eastern chipmunks and white -footed mice: Population histories since the last glacial maximum

This study examined the demographic and biogeographic history of eastern chipmunks (Tamias striatus) and white-footed mice ( Peromyscus leucopus) in the central United States. Mitochondrial DNA variation was linked to the colonization history of populations into the region since the last glacial maximum (LGM). In addition, microsatellite variation from P. leucopus was used to evaluate the importance of human landscape alteration in disrupting gene flow among populations.;Multiple geographically structured monophyletic mitochondrial DNA lineages were recovered for both species that were not concordant with contemporary biogeographic barriers. In addition, variation within each of these lineages suggested that populations have expanded into the region since the LGM.;These data also suggest that T. striatus and P. leucopus populations expanded from shared refugial locations indicating a long history of association for these two species in this region. Four major mitochondrial DNA lineages with similar distributions were recovered for both species. The 'western' lineages of T. striatus and P. leucopus, in particular, exhibited nearly identical distributions limited almost entirely to Wisconsin and Illinois. The western lineages appear to have expanded south from a northern refugium, contrary to traditional predictions that species would have expanded north from a southern refugium following glacial recession. The distribution of the western lineages also was concordant with the distribution of oak-savannah deciduous forest formations suggesting that this association reflects a shared geographic history of isolation and post-glacial expansion for many deciduous forest species.;Finally, analyses of variation at 6 microsatellite loci among 210 P. leucopus from three sites each around three of the largest cities in Illinois recovered reduced levels of gene flow among sites separated by urban development compared to sites separated by deciduous forest habitat. Mitochondrial DNA sequences of all P. leucopus indicated that post-glacial expansions into the region did not confound the analysis of microsatellite variation. This study provides important empirical data on the importance of urban development in disrupting evolutionary processes within natural populations.