Phylogeography and evolution of the triplefin Tripterygion delaisi (Pisces, Blennioidei)

The genus Tripterygion (Risso 1826) is restricted to the eastern Atlantic and the Mediterra- nean, and comprises only three species. T. melanuros and T. tripteronotus are essentially endemic to the Mediterranean, while Tripterygion delaisi occurs in the Atlantic and in the Mediterranean. Two subspecies of T. delaisi have been described (T. d. xanthosoma in the Mediterranean and T. d. delaisi in the Atlantic). Sev- eral scenarios have been proposed for the evolution of T. delaisi subspecies, but so far its subspeciation pro- cess is not clear. In this study we present a population survey of T. delaisi including specimens from the two recognized subspecies. We combined a phylogeo- graphic approach with estimates of the direction of migration (between the Atlantic and the Mediterra- nean) and of the coalescence time of the two subspe- cies, using polymorphic mitochondrial and nuclear genes. The results of this study clearly support the exis- tence of two Tripterygion delaisi clades, one in the east- ern Atlantic islands and another in the Atlantic coasts of Europe and in the Mediterranean. Historical migra- tion between the islands and Western Europe plus Mediterranean was restricted, and showed a west- bound trend, with a higher number of migrants going from the Western Europe plus Mediterranean into the islands. We estimated the time of coalescence of both groups of T. delaisi to be more recent than the onset of Pleistocene glaciations (1.7 Mya). Our results are con- sistent with previous hypothesis that consider succes- sive dispersal events of a Tripterygion ancestor from the western African coast colonizing the Atlantic islands and the Mediterranean, promoting the evolu- tionary divergence between these areas.