Molecular phylogeography of Dryas integrifolia: glacial refugia and postglacial recolonization

Chloroplast DNA variation in the Arctic plant species Dryas integrifolia (R osaceae) was analysed in relation to both the present-day geographical dist ribution of populations and to Pleistocene fossil records of this species. The phylogeographical structure was weak but the analysis of haplotype dive rsity revealed several groups of haplotypes having present-day geographical ranges that overlap locations postulated from geographical and fossil evid ence to have been glacial refugia. Based on this information we infer that two important refugial sources of Arctic recolonization by this species wer e Beringia and the High Arctic. Two other putative refugia, located southea st of the ice sheet and along coastal regions of the eastern Arctic may hav e served as sources for recolonization of smaller portions of the Arctic. T he genetic substructure in the species is mostly due to variation among pop ulations regardless of the ecogeographical region in which they are found. Spatial autocorrelation at the regional scale was also detected. High level s of diversity both within populations and ecogeographical regions are prob ably indicative of population establishment from several sources possibly c ombined with recent gene flow.