The effects of Quarternary ice ages on the historical demography of a North American species group of tiger beetles (Coleoptera: Carabidae: Cicindelinae)

Glaciation-interglaciation cycles have had profound affects on the genetic variation of populations and species. Phylogeographic studies in North America have typically focused on vertebrate taxa, with fewer examining broad patterns in insects. More detailed studies across a broader range of taxa are needed for a comparative approach to understand the effects of Quarternary climate change on North America. For this study, we thoroughly sampled a monophyletic group of five North American tiger beetles that are collectively distributed throughout most of the continent, including extensive areas that are known to have been affected by glaciations. MtDNA sequences were obtained from 514 individuals representing all species and 130 sampled populations and we employed phylogenetic, population genetic and coalescent-based analyses to investigate specific historic demographic patterns in this group of climatically sensitive insects. Species were found to be polyphyletic, yet deeply divergence mtDNA clades were recovered. The geographic locations of these were consistent with previously hypothesized glacial refugia. Clear patterns of historical subdivison and subsequent demographic expansion were observed, but differed throughout the group. Furthermore, the genetic patterns revealed a strong correlation between elevation, latitude, and genetic structuring.