Phylogeography of the ocellated skink Chalcides ocellatus (Squamata, Scincidae), with the use of mtDNA sequences: a hitch-hiker's guide to the Mediterranean.

We analyze geographic genetic variation in C. ocellatus to evaluate the influences of major climatic, paleogeographic and anthropogenic factors in its biogeographic history. Ninety four specimens from 61 populations were collected across all of its geographical range and analyzed based on partial mitochondrial sequences (cyt b, 12S, and ND1). Our results demonstrate that an ancestral form of C. ocellatus, which expanded in northwestern Africa at the end of Miocene, diverged in at least three separate evolutionary lineages approximately 4.57Ma: C. humilis spread south of the Sahara, while the other two (C. ocellatus sensu stricto) were restricted in the coastal North African region. The complicated history of the ocellated skink is a result of multiple vicariant phenomena followed by multiple active or passive dispersals. The Messinian salinity crisis and the re-flooding of the Mediterranean basin, the climatic transition from Middle to Upper Pliocene, and the hyperarid phase of the Sahara, affected the distribution and diversification of C. ocellatus, while in historical times it was introduced in the central Mediterranean islands and eastern Mediterranean region from Tunisia and Cyrenaica, respectively.