Aim The intricate puzzle-like geography of the western Mediterranean is a product of long-term tectonic and orogenic events, supplemented by repeated climatic oscillations since the Pliocene. It offers numerous vicariance events that may be invoked to explain speciation in amphibians. We test for plausibility of two mutually exclusive Iberian–African vicariance hypotheses to explain the basal split within newts of the genus Pleurodeles: (1) the disconnection of the Betic arch c. 14 Ma and (2) the end of the Messinian salinity crisis 5.33 Ma.
Location Specimens of P. waltl and P. poireti were sampled from 32 populations in Portugal, Spain, Morocco, Algeria and Tunisia.
Methods Parts of three mitochondrial genes were sequenced (16S rRNA, cytochrome b, ATPase). Based on substitution rate constancy among lineages three different molecular clocks were calibrated to derive competing evolutionary scenarios for lineage evolution within Pleurodeles.
Results One scenario was aligned with the dated fossil record and with historical events that are known to have enabled terrestrial faunal exchange between Europe and Africa. In Pleurodeles, such faunal exchange is more likely to have happened three times, resulting in the current pattern of species diversity and haplotype distribution: (1) following the disconnection of the Betic region from Iberia and connection of its southernmost part (present-day Rif Mountains) to Africa, c. 14 Ma; (2) closing of the Strait of Gibraltar prior to the Messinian salinity crisis, 5.59–5.33 Ma; (3) passive dispersal in recent times, caused by rafting on vegetation or inadvertent displacement by man. The results show that North African P. poireti populations comprise two distinct lineages; despite their geographical proximity, haplotype distribution within both lineages indicates totally different histories (range fragmentation vs. dispersal).
Main conclusions Ribbed salamanders mainly evolved through allopatric speciation, driven by vicariance events. However, faunal exchange between Europe and Africa at the western end of the Mediterranean basin was linked to well-known events of physical contact between both continents. This sheds new light on the potential role of dispersal across marine barriers via rafting or even, presumably inadvertent, anthropogenic displacement for the initiation of speciation in amphibians.