Microsatellite analysis of red mullet Mullus barbatus (Perciformes, Mullidae) reveals the isolation of the Adriatic Basin in the Mediterranean Sea

The red mullet Mullus barbatus is commercially one of the most important demersal fish resources in the Mediterranean. Moleculardata on its genetic population structure throughout the Mediterranean are reported. Six microsatellite loci displayed a high degree ofexpected heterozygosity and a high allele number per locus. The Hardy–Weinberg equilibrium test revealed an overall tendencytowards heterozygote deficiency, probably caused by the admixture of various demes. Population differentiation was assessed by analysisof molecular variance (AMOVA) and Bayesian analysis. AMOVA showed that most of the variation was within the population, butthe mean value of FST was significant, indicating genetic differentiation among the samples analysed. This differentiation is primarilyattributable to the isolation of the Adriatic samples and partly to a weaker substructuring of the populations in the Gulf of Lions,Tyrrhenian Sea, Strait of Sicily, and Ionian Sea. Bayesian analysis also revealed genetic differentiation among the samples analysed, identifyingtwo genetic clusters. The restricted gene flow from and to the Adriatic, also recorded for other fish species, most likely reflectsthe environmental separation of the Adriatic and suggests that management protocols for the red mullet in the Mediterranean shouldbe revisited.