The Stock Genetic Structure of Two Sparidae Species, Diplodus vulgaris and Lithognathus mormyrus, in the Mediterranean Sea.

Polyacrilamide gel electrophoresis (PAGE) of allozymes was used to investigate the intraspecies genetic variation andthe genetic stock structure of Diplodus vulgaris and Lithognathus mormyrus captured from eight localities in the MediterraneanSea. Twenty-two and 20 putative enzyme-coding loci were examined, respectively, in D. vulgaris and L. mormyrus.Polymorphic loci at the 95% level were used to assess the allozyme variability in D. vulgaris (AAT-2, EST-1, GLDH,PEPB-2, PGI-2, PGM, SDH) and L. mormyrus (AAT-2, EST-1, GLDH, MDH-2, PGI-2, PGM). The proportionof polymorphic loci in both species ranged from 0.31 (D. vulgaris) to 0.30 (L. mormyrus), and the observed and expectedmean heterozygosity varied between 0.082 and 0.093 (D. vulgaris) and between 0.069 and 0.072 (L. mormyrus). The meanvalue of observed heterozygosity in D. vulgaris showed a deficit of heterozygosites, thereby indicating a Wahlund effectin the samples examined. Significant genetic differentiation (mean value of θ = 0.013, p < 0.005) was found in D.vulgaris indicating an intraspecific genetic substructure among the samples examined, whereas the mean value of θ = 0.001, p > 0.05 found in L. mormyrus showed a high degree of genetic homogeneity. The results showed the presenceof distinct subpopulations of D. vulgaris among the sampled sites, and suggested that analysis of allozymes may provideimportant information on the genetic stock structure of these two sparids to ensure sustainable management of thesespecies.