Low levels of population genetic structure in the gilthead sea bream, Sparus aurata, along the coast of Italy

Abstract

The gilthead sea bream, Sparus aurata, is a coastal, commercially important fish. Contrasting results concerning the genetic structure of the species at different geographic scales have been reported. Here, an investigation is made into the population genetic structure of S. aurata along the coast of Italy, using samples analysed previously and material from new sampling sites (12) and using different microsatellite loci (10). One sample from the eastern Atlantic and three temporal replicates from one site were also included. The presence of a weak (overall FST = 0.0072), but significant, genetic population subdivision was detected by F-statistics. Temporal replicates indicate genetic data consistency over time. Isolation by distance between the Atlantic and the coast of Italy is suggested by a Mantel test. The distributional pattern of genetic variance obtained by analysis of molecular variation reflects the geographic sampling areas, but is only partially congruent with the results obtained with fewer sites and loci. The dispersal of passive eggs/larvae by the main currents appears to contribute to shaping the gene flow. Given the intensity of sea bream aquaculture activities in Italy, the possibility that aquaculture may have partially contributed to the population genetic pattern detected cannot be excluded.