Increased genetic structuring of isolatedSalamandra salamandrapopulations (Caudata: Salamandridae) at the margins of the Carpathian Mountains

Abstract

The traditional southern Pleistocene refugia hypothesis in Europe has lately been challenged for several animal and plant species. The Carpathian Basin, especially at the marginal regions, is one of the recently recognized biodiversity hotspots in Europe. Marginal populations are prone to have lower genetic diversity and higher genetic differentiation than central populations. Here, we examined one mitochondrial DNA fragment (D-loop) and nine nuclear (microsatellite) loci to describe the genetic diversity and phylogeographical pattern of fire salamander (Salamandra salamandra) populations in the Carpathian Basin with focusing on the southern margins of the Western Carpathians, where isolated populations of this species are present. Analyses of microsatellites indicated reduced genetic diversity for most of the isolated populations. Based on the mitochondrial DNA, only two haplotypes were found, whereas the analyses with the nuclear markers revealed a more recent genetic split between Western (Alpine) and Eastern (Carpathian) populations, and separated the Apuseni Mountains population (part of the Western Carpathians). Using approximate Bayesian computation analyses, we identified the most probable colonization scenario for the isolated North Hungarian Carpathian Basin populations. The split between isolated salamander populations from the central populations in the Carpathian Mountains dates back to the beginning of the Late Pleistocene, while the split between most of the Hungarian populations can be associated with the Last Glacial Maximum. We found evidence for long-time isolation between the marginal Carpathian Basin and central populations. Our results also show that S. salamandra survived glacial periods in the temperate forests of north-east Pannonia (North Hungarian Mountains), confirming that the Carpathian Basin served as important northerly refugia during the Pleistocene climatic oscillations.