Molecular markers, natural history and evolution in sharks and rays

Chondrichthyes are an ancient class of cartilaginous fishes, whose systematic and bio-ecological features make them contemporaneously specious and at high risk of extinction. Large sampling efforts carried out in the Mediterranean and Eastern Atlantic for several years provided the unique opportunity to build up unprecedented repositories of vouchers for exploring genetic variation from population to family levels. Difficulties in species identification linked to high levels of morphological stasis were overcame by wide-scale DNA barcoding analysis of Mediterranean chondrichthian fauna (coverage at 50%) improving species assessment and fostering conservation and management actions. Phylogenetic relationships and historical biogeography of Mediterranean, Eastern Atlantic and Indian Ocean skates (Rajidae) have been reconstructed using concatenated mtDNA genes revealing patterns of antipodean allopatric parallel speciation strictly correlated to a pan-biogeographical (vicariance) model. Coupling integrated panels of unisexually and bisexually inherited markers and large scale sampling of historical and contemporary populations of threatened and endangered sharks and skates permitted to reveal several cryptic speciation events, strong phylogeographical and population structure unexpected in marine realm disentangling natural and phylogenetic histories and allowing the practical identification of conservation and management units.