Novel insights into the origin of Mediterranean Great White Shark population from ancient mtDNA gene variation

The origin of a population of great white sharks (GWS), Carcharodon carcharias, L.1758, residing in the Mediterranean Sea has remained a mystery despite repeated scientific endeavours to retrace their history. Here we analyze 18 historical specimens (30-180 years old) collected from several museums, research institutes and private collections in Italy, creating the largest dataset of Mediterranean GWS mitochondrial DNA gene sequences (i.e. D-loop and COI). Comparative phylogenetic analyses of the Mediterranean GWS with populations from global range suggested a closer evolutionary relationship with sharks in Australia- New Zealand, Japan and the Pacific US rather than to the South-African population. Estimates of the most recent common ancestor carried out using internal calibration with fossil and paleo-geographical data revealed that Mediterranean GWS population originated in the early Pliocene at the end of the Messinian Salinity Crisis (ca. 5.3 MYA). This dating supports a GWS historical long-dispersal and paleo-colonization of the Mediterranean via a route of migration through Central America, before the formation of the Isthmus of Panama in contrast with a ad hoc previous hypothesis which suggested a colonization via South Africa due to navigational errors during past climatic oscillations.