It makes a difference who you are: first record of Dasyatis tortonesei Capapé, 1975 along Sardinian coasts and taxonomic uncertainties within stingrays

Despite several records of Dasyatis tortonesei Capapé, 1975 in the Mediterranean Sea, its distribution and abundance have been questioned due to the cryptic nature of the Tortonese’s stingray and the frequent misidentification with the common stingray Dasyatis pastinaca (Linnaeus, 1758). Through morphological and molecular analyses, the two species had been confirmed in previous studies, but uncertainties remain about their distribution and presence, and the effectiveness of morphological and molecular discrimination between these two stingrays. Additionally, D. tortonesei suffers from limited availability of biological information, in part due to the abovementioned taxonomic ambiguity, hampering adequate conservation actions. In fact, D. tortonesei is listed as Data Deficient on the International Union for Conservation of Nature (IUCN) Red List, while D. pastinaca is classified as Vulnerable. The catching of an “unusual” stingray along the Sardinian coast led us to hypothesize that it could be a D. tortonesei individual. Since the correct identification of specimens is necessary to properly assess the impact of fisheries, and stingrays share many morphological similarities, molecular identification of this specimen was conducted using mtDNA markers. Additional specimens of stingrays were sampled in the same area. New and public sequences of COI and NADH2 mito-chondrial genes were analysed. Sequence data confirmed the occurrence of D. tortonesei in the investigated area, highlighting the frequent misidentification between this species and closely related species in the field, and underscoring the need for updated and reliable morphological identification keys. To evaluate whether the misidentification issue involves other Mediterranean stingrays, an extensive molecular analysis, including multiple species, was performed. The application of several species-delimitation methods revealed widespread taxonomic uncertainties across the five genera of the Mediterranean Dasyatidae. These results point out unresolved systematic issues within the family and emphasize the urgent need for further integrative taxonomic studies and a comprehensive revision of the taxon, essential to support effective conservation strategies.