A combined genetic-morphometric analysis unravels the complex biogeographical history of Polyommatus icarus and Polyommatus celina Common Blue butterflies

Widespread species have the potential to reveal large-scale biogeographical patterns, as well as responses to environmental changes possibly unique to habitat generalists. This study presents a continental-scale phylogeographical analysis of Polyommatus icarus, one of the most common Palaearctic butterflies, and the morphologically and ecologically similar Polyommatus celina, a recently discovered cryptic species. By combining data from mitochondrial [cytochrome c oxidase subunit I (COI)] and nuclear [internal transcribed spacer (ITS2)] molecular markers with geometric morphometrics, we document a complex phylogeographical history for the two species. Despite morphological similarities, the genetic divergence between these two species is high (more than 5% at COI) and they are not sister species.