Comparing patterns of nuclear and mitochondrial divergence in a cryptic species complex: the case of Iberian and North African wall lizards (Podarcis, Lacertidae)

Combining different sources of information is essential for a complete understanding of the process of genetic differentiation between species. The Iberian and North African wall lizard ( Podarcis ) species complex has been the object of several studies regarding morphological and mitochondrial DNA variation but, so far, no large-scale survey of nuclear variation within this group has been accomplished. In this study, ten polymorphic allozyme loci were studied in 569 individuals collected across the Iberian Peninsula and North Africa. The obtained data were analysed using both conventional population genetic tools and recent Bayesian model-based clustering methods. Our results show that there are several well-differentiated entities corroborating the major splits observed in mtDNA analyses. These groups correspond not only to the fully recognized species Podarcis bocagei , Podarcis carbonelli , and Podarcis vaucheri but also to multiple forms within the polytypic Podarcis hispanica , all of which have a similar level of differentiation to that observed between the acknowledged species. However, relationships between forms are weakly supported both by population and individual clustering methods, suggesting a scenario of a rapid diversification that contrasts to the clear bifurcating model assumed from previous mtDNA analyses. Individual multilocus analyses report few individuals misassigned or apparently admixed, some of which are most likely explained by the persistence of high levels of ancestral polymorphism. Other admixed individuals, however, are probably the result of limited levels of gene flow between forms.  © 2007 The Linnean Society of London, Biological Journal of the Linnean Society , 2007, 91 , 121–133.