Population Genetic Structure in Eastern Chipmunks at Pennsylvania State U niversity on M ay 11, 2016 http://jhered.oxfordjournals.org/ D ow nloaded from Goudet

Dispersal and gene flow are important processes affecting the evolutionary potential of wild populations. Assessing the importance of such patterns is thus critical, especially in contexts where environmental attributes may enhance or restrict the movements of individuals across patchy habitats. A landscape genetics approach is effective in that respect as it combines spatial and genetic data to identify landscape features that play a role in shaping genetic structure. The primary objective of our research was to characterize the determinants of population genetic structure in the eastern chipmunk (Tamias striatus) over a large heterogeneous study area in southern Quebec and Ontario, Canada. We genotyped 572 individuals using 7 microsatellites loci and found an average FST of 0.127 ± 0.035 among our 7 sampling sites. We found evidence that major rivers act as important barriers to gene flow at a large scale. We also detected a signal of male-biased gene flow at all scales considered. Our findings highlight the importance of simultaneously taking into account landscape elements and geographic distance, considering the scale at which determinants of genetic structure may act and using the appropriate measures to detect sex-biased dispersal based on the characteristics of the sampling design. Key words: genetic differentiation, isolation by distance, landscape genetics, microsatellite loci, sex-biased dispersal, Tamias striatus Identifying and explaining patterns of population genetic structure in natural populations is vital for our understand