Speciation in mountains: phylogeography and phylogeny of the rock lizards genus Iberolacerta (Reptilia: Lacertidae)

Abstract

The vertebrate faunas in Southern Europe have a higher specific richness than in central and northern Europe and a high level of endemism (see, e.g., Baquero and Telleria, 2001; Meliadou and Troumbis, 1997), both probably related to the presence of faunal refugia during the Pleistocene glacial episodes (Hewitt, 1996, 1999; Taberlet et al., 1998). This scenario implies that the Pleistocene glacial oscillations are responsible for the current geographic distribution of species, but not that speciation events producing the contemporary species occurred at the same time. Indeed, genetic divergences between temperate vertebrate species imply that most diverged before the Pleistocene (Avise et al., 1998; Johns and Avise, 1998). Under this hypothesis, the high levels of species richness and endemism in Southern Europe would result from lower extinction rates in these areas during glacial maxima (refuge effect) combined with limited dispersal capabilities of non-avian vertebrates which prevented some of them to colonise Northern and Central Europe. A non-exclusive hypothesis relates the higher species richness in southern European peninsulas to the complex topography and history of these areas, their numerous mountains providing separated habitats where populations would be isolated following colonisation events (Garc ia-Barros et al., 2002). The Iberian rock lizards of the genus Iberolacerta Arribas, 1997 constitute a promising model to evaluate these biogeographical scenarios, since they are restricted