The biogeography of the western Mediterranean: elucidating contradictory distribution patterns of differentiation in Maniola jurtina (Lepidoptera: Nymphalidae)

In the western Palaearctic, the Mediterranean zone is an important region where taxa and genes of thermophilous organisms are preserved during glacial stages and new clades are generated. This is achieved through the existence of refugia over Mediterranean Europe and North Africa, where organisms persisted and continued to evolve during the cold phases. However, it is not clear in detail how these refugia function for the maintenance of ancestral taxa, the evolution of new taxa, and as launching pads during postglacial colonizations of northern Europe. One outstanding issue is the incongruence of findings from different marker systems. For the butterfly Maniola jurtina, morphometry and allozyme data analyzed for populations scattered over Europe and North Africa show congruent patterns for Sicily and the Maghreb but produce discrepant results for the Italian mainland. This discrepancy between allozyme and morphological data can be explained by recent gene flow in the wake of postglacial range expansions and shifts. It is evident that colonization histories are far more complex than originally considered. We highlight different aspects of colonization and evolutionary history emerging from the joint use of different marker systems and advocate multiple uses of different markers in paleobiogeographic reconstructions to explore evolutionary events and colonization pathways.