Phylogeography of Helleria brevicornis (Crustacea, Oniscidea): old and recent differentiations of an ancient lineage.

Helleria brevicornis has a disjunct, peri-Tyrrhenian distribution that mirrors that of several organisms, for which geographic vicariance is invoked, due to the geological events started with the Oligocene split of the Sardo-Corsican microplate from the Pyrenees, and successive separation between Sardinia and Corsica. Molecular phylogenetic analyses demonstrated that such a biogeographic model does not apply to Helleria. The original split of the Sardinian and Corsican lineages originated in the Early Pliocene. Further diversification occurred later. The colonization of the Tuscan archipelago, French, and Italian mainland occurred most recently, but a possible time dependency bias suggests that such colonization was driven by human-transport.