Recent evolutionary history of the Iberian endemic lizards Podarcis bocagei (Seoane, 1884) and Podarcis carbonelli Pérez-Mellado, 1981 (Squamata: Lacertidae) revealed by allozyme and microsatellite markers

Abstract

Podarcis bocagei and Podarcis carbonelli are two species of wall lizards endemic to the western Iberian Peninsula. A detailed phylogeographical study based on mitochondrial DNA (mtDNA) variation has shown that they responded differently to the Quaternary climatic oscillations. These differences have been attributed to their distribution patterns: P. bocagei is distributed in the north of the Peninsula and in a continuous fashion, whereas P. carbonelli has a more southern and fragmented distribution. In this study, we assessed whether nuclear markers reveal similar evolutionary patterns to those inferred from mtDNA variation. We studied a battery of allozyme and microsatellite loci in a geographically representative set of individuals from both species. For each species we evaluated overall levels of differentiation, patterns of geographical variation in genetic diversity, genetic relationships amongst localities, and applied model-based individual multilocus genotype clustering approaches to detect hidden population structure. Our results for P. bocagei are highly concordant with the phylogeographical scenario inferred from mtDNA variation: we found very low levels of population differentiation, consistent with survival in a single glacial refugium, and detected signatures of a rapid demographic and geographical expansion. The analyses of nuclear markers furthermore helped to identify a probable refugial area, as well as expansion routes. Additionally, in concordance with observations based on mtDNA variation, a low level of population differentiation was observed in P. carbonelli, but this was significantly higher than in P. bocagei. However, the geographical basis for differentiation in P. carbonelli is highly inconsistent between mtDNA and nuclear markers, suggesting a complex, albeit recent, history of fragmentation. A recent reduction of this species’ distribution has probably erased the signatures of glacial isolation and post-glacial expansion that are normally found in other Iberian species, suggesting that the currently observed pattern of genetic differentiation in this species was shaped more by recent genetic drift than by the Pleistocene climatic oscillations.