Historical biogeography and local adaptation explain population genetic structure in a widespread terrestrial orchid.

Forests in the Mediterranean and Carpathians likely acted as glacial refugia for Epipactis helleborine. Postglacial migration northwards and to higher elevations resulted in the dispersal and diversification of E. helleborine in central Europe and Italy, as well as geographic isolation and divergent adaptation in Greek and Italian populations. Distinguishing adaptive from neutral genetic diversity allowed us to conclude that E. helleborine has a high adaptive potential to climate change and demonstrates that signals of adaptation and historic isolation can be identified even in species with high gene flow.