Biodiversity of dogfishes (genus Squalus) in the eastern Atlantic and Mediterranean Sea - a molecular perspective

V Jornadas Ibéricas de Ictiología SIBIC, Conhecer para preservar, 24-27 June 2014, Lisboa .-- 1 page
The genus Squalus, or dogfishes, includes many coastal shark species commonly caught in commercial fisheries around the world. Despite their abundance, species diversity within Squalus is still poorly understood. In fact, recent studies on the Indo-Pacific region have described several new species, highlighting the need for revisionary taxonomic work clarifying and discriminating the different taxa. Less attention has been paid to the diversity of Squalus in the Atlantic Ocean sensu lato, where only five species have been reported out of the 27 species currently accepted for the genus, namely S. acanthias, S. blainville, S. megalops, S. mitsukurii, and S. cubensis. Notwithstanding, species identification across the region appears to be very inconsistent and there is great taxonomic uncertainty among some of the Atlantic Squalus, particularly concerning the status of S. megalops and S. blainville. This situation has contributed to the present confusion in terms of the actual species composition in the region, thus compromising the effectiveness and adequacy of any management and conservation efforts. In an initial effort to contribute to a comprehensive and clear alpha taxonomy of this highly diverse worldwidedistributed genus, we applied molecular genetic markers (mitochondrial cytochrome oxidase I and NADHdehydrogenase 2) aiming to evaluate the number of discrete genetic lineages within Squalus in the eastern Atlantic and Mediterranean Sea. Furthermore, we compared this regional lineage diversity to that found worldwide, using publicly available data. Our results confirm the inconsistencies in species identification in the eastern Atlantic and Mediterranean. For instance, putative S. blainville and S. megalops sampled across the Mediterranean and along the eastern Atlantic from Portugal to South Africa clustered together in a single clade, sister to the clade of the Australian S. megalops (i.e. from the type location). Our data also indicate the presence of three highly divergent genetic lineages of Squalus in the Mediterranean Sea, comprising three distinct species. Furthermore, we found evidence of the presence of the S. cubensis lineage (currently described only for the western Atlantic) in the equatorial eastern Atlantic