DNA barcoding of atlantic skates (Chondrichthyes, Rajiformes): taxonomic and phylogeographic inferences and conservation impacts

Anthropogenic impacts are responsible for alarming declines in the abundance and distribution of several marine species. Their future conservation and long-term management plans need to be conceived upon a universally recognised key-feature: species identity. In the past, this important assignment resulted particularly arduous among skates (Rajiformes), in which the phenotypic similarity between some taxa and the individual variability in others, entangled accurate species identification. This research project aimed to confirm the power of DNA barcoding for the discrimination between skate species across the Atlantic Ocean and for its use as effective tool to minimize the risk of species misidentification. In this perspective, this work aimed to compile a new and fully available barcode library, the ELASMO-ATL project, which gathered biological and molecular information of Atlantic rajid fauna. In addition, considering the vast geographical distribution of six species, this study investigated whether the mitochondrial gene Cytochrome Oxidase subunit I (COI) can preliminarily identify potential geographical populations. DNA barcodes were obtained from 398 individuals collected during past scientific surveys across four main FAO divisions (FAO 27, FAO 34, FAO 41 and FAO 47), obtained data successfully resolved many taxonomic ambiguities and demonstrated a highly cohesive monophyletic clustering within the order, as well as a high number of concordant Barcode Index Number (BINs). Further inference of evolutionary patterns suitable for addressing management and conservation issues should be undertaken considering the six species selected for the phylogeographic analysis. In conclusion, a well-curated barcode library was established and this novel resource provides samples, specimens information and corresponding reference sequences of the group in question for future studies.