Erebia epiphron and Erebia orientalis: sibling butterfly species with contrasting histories

The butterfly genus Erebia (Lepidoptera: Nymphalidae) is the most diverse in Europe and comprises boreo-alpine habitat specialists. Populations are typically fragmented, restricted to high altitudes in one or several mountain ranges, where habitat is relatively well preserved, but where the effects of climate change are considerable. As a result, the genus Erebia has become a model to study the impact of climate changes, past and present, on intraspecific genetic diversity. In this study, we inferred phylogenetic relationships among populations of the European species Erebia epiphron and Erebia orientalis using mitochondrial (COI) and nuclear markers (ITS2, wg and RPS5), and reconstructed their phylogeographical history. We confirm E. orientalis and E. epiphron as a relatively young species pair that split c. 1.53 (+/- 0.65) Mya. The high genetic homogeneity of E. orientalis, combined with its restricted geographical range in the eastern Balkans, suggests that this taxon may be subject to inbreeding depression and displays low adaptability to potential environmental changes, which calls for close monitoring of population trends. By contrast, genetic structure was complex for E. epiphron, revealing an intricate phylogeographical history that included a succession of dispersal events, mixing of populations and periods of isolation in multiple refugia. Finally, we highlight southern populations that represent unique genetic lineages, which, in the case of extinction, would lead to important genetic erosion.