Two markers and one history:: phylogeography of the edible common sea urchin Paracentrotus lividus in the Lusitanian region

Benthic marine invertebrates with long-lived larvae are believed to have dispersal capabilities that contribute to maintaining genetic uniformity among populations over large geographical scales. However, both hydrological and biological factors may limit the actual dispersal of such larvae. We studied the population genetic structure of the edible common sea urchin Paracentrotus lividus (Lamarck, 1816), to explore its dispersal patterns in the Atlanto-Mediterranean region and, more specifically, to ascertain the role of the Strait of Gibraltar in shaping the genetic structure of this species. For this purpose, we analysed 158 individuals for the mitochondrial 16S rRNA gene and 151 of these for the nuclear single-copy intron adenine nucleotide transporter (ANT) from 16 localities from the Atlantic and Mediterranean basins, spanning over 4,000 km. Mitochondrial 16S rRNA shows higher genetic diversity in the Mediterranean than in the Atlantic and reveals a sharp break between the populations of both basins, probably as a consequence of the barrier imposed by the Almeria-Oran hydrological front, situated east of the Strait of Gibraltar. Both markers suggest that a recent population expansion has taken place in both basins, most probably following the Messinian salinity crisis.