Mitochondrial DNA reveals high genetic divergence between populations of Chalcides mertensi Klausewitz, 1954 (Reptilia: Scincidae) from Tunisia

Genetic diversity of four populations of Chalcides mertensi (Klausewitz, 1954) from Tunisia was analyzed by means of the Restriction Fragment Length Polymorphism (RFLP) analysis of two fragments of mitochondrial DNA (mtDNA) encompassing NADH dehydrogenase subunits 1 and 2 (ND-1/2) and NADH dehydrogenase subunits 3, 4 and 4L (ND-3/4). Phylogenetic relationships between haplotypes were inferred by analysing the sequence of 396 base pairs at the 5' end of the mitochondrial gene encoding cytochrome b and a segment of 12S rRNA gene (386 bp). The results of this study highlighted a pronounced genetic divergence between the populations from northern (Ain Soltane and Tabarka) and southern (Kasserine and Sidi Bouzid) Tunisia, that the phylogenetic analysis recovered as two distinct taxonomic entities. These two groups of populations can therefore be ascribed to two distinct taxa, with southern populations probably representing the typical C. mertensi, whereas northern individuals are likely to represent a new species of grass swimming Chalcides. The divergence between these two taxonomic entities can be referred to palaeogeographic and palaeoclimatic events that have affected northwestern Africa during the last 10 Million years. The analysed populations show a low genetic variability that can be related to the past climatic and geologic events and the colonization processes that took place with environmental amelioration, and to the peripheral position of these populations in the distributional range of the species. However, a more exhaustive study, including Algerian and Moroccan skink populations will be necessary in order to clarify these issues.