Two seas, two lineages: How genetic diversity is structured in Atlanticand Mediterranean greater amberjack Seriola dumerili Risso, 1810 (Perciformes, Carangidae)

The vastness of the ocean and our limited ability to observe and monitor the organisms therein makemolecular markers particularly useful tools in the investigation of the ecology and evolutionary biologyof fish. Nowadays, due to increased demand of fish foods, genetic researches are focused on new can-didate species for aquaculture, such as Seriola species. Here, the analyses of eight polymorphic nuclearmicrosatellites loci and three mitochondrial (mt) DNA genes (16S-rRNA, Cyt-b, and D-Loop) in the greateramberjack, Seriola dumerili, detected breakpoint between Atlantic and Mediterranean populations, pre-sumably arisen by the oceanographic features of the Almeria-Oran Front opposed to the gene flow of thespecies. Still, an absence of heterogeneity between the sampling locations within the Mediterranean Seawas noted, although an observed dichotomous structure of the phylogenetic mtDNA tree revealed twoclades, with no spatial division within the basin. The origin of these two clades likely predates the latePleistocene or Holocene colonization of the species from the Atlantic Ocean into the Mediterranean Sea.In addition, some preliminary genetic information are provided for Seriola rivoliana, the species that hasbeen recently recognized as an Atlantic migrant in the Mediterranean.