Teresa Maggio

The stock genetic structure of two Sparidae species, Diplodus vulgaris and Lithognathus mormyrus, in the Mediterranean Sea

Abstract Polyacrilamide gel electrophoresis (PAGE) of allozymes was used to investigate the intraspecies genetic variation and the genetic stock structure of Diplodus vulgaris and Lithognathus mormyrus captured from eight localities in the Mediterranean Sea. 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 proportion of polymorphic loci in both species ranged from 0.31 ( D. vulgaris ) to 0.30 ( L. mormyrus ), and the observed and expected mean heterozygosity varied between 0.082 and 0.093 ( D. vulgaris ) and between 0.069 and 0.072 ( L. mormyrus ). The mean value of observed heterozygosity in D. vulgaris showed a deficit of heterozygosites, thereby indicating a Wahlund effect in the samples examined. Significant genetic differentiation (mean value of θ =0.013, p 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 presence of distinct subpopulations of D. vulgaris among the sampled sites, and suggested that analysis of allozymes may provide important information on the genetic stock structure of these two sparids to ensure sustainable management of these species.

Genetic population structure of Epinephelus marginatus (Pisces, Serranidae) revealed by two molecular markers

In this paper, data are presented regarding the population structure of dusky grouper (Epinephelus marginatus) which was sampled in the Mediterranean Sea and Atlantic Ocean using two different molecular markers, ND2 RFLP and cytochrome b (cyt b) sequence analysis. The main objective of the study is to analyse the genetic variability of E. marginatus in the Mediterranean Sea to define how the biological characteristics of the species, such as the dispersal capability of pelagic larvae and the benthonic‐sedentary life style, can affect the genetic population structure or maintaining the gene flow or determining genetic differences. Furthermore, we considered an Atlantic sample to establish the presence of genetic differences between the two biogeographical areas under consideration. Analysis of variation based on ND2 RFLP analysis revealed a genetic difference between the Atlantic and Mediterranean samples, whilst cyt b sequence analysis did not. There exists evidence for genetic differentiation for both molecular markers in the Mediterranean region. The majority of the variation was due to the Ustica Island sample and this could be due to differences in fisheries effort since the island is a protected area where recreational and professional fisheries are almost completely forbidden. The pattern of genetic diversity, haplotype networks and mismatch distribution suggest a historical influence on the genetic structure of E. marginatus and recent population expansion. An analysis of the genetic structure of the dusky grouper will be the prerequisite for decisions regarding conservation and fisheries management.

Further investigations on populations of the deep-water blue and red shrimp Aristeus antennatus (Risso, 1816) (Decapoda, Dendrobranchiata), as inferred from Amplified Fragment Length Polymorphism (AFLP) and mtDNA analyses

The aim of this study was to integrate existing mitochondrial DNA data relating to the deep-sea blue and red shrimp Aristeus antennatus (Risso, 1816) with data obtained by Amplified Fragment Length Polymorphism (AFLP). A total of 145 AFLP polymorphic loci were scored in 236 specimens collected from one Atlantic and seven Mediterranean sample sites. AMOVA results revealed that the overall genetic variation among-populations was lower (11.81%) than within-populations (88.19%). The genetic variation between the Atlantic and Mediterranean samples was found to be not significant ( Φ CT = − 0 . 007 ; N.S.), indicating that the transition area between the Atlantic Ocean and the Mediterranean Sea does not act as a barrier to gene flow. Bayesian analysis also demonstrated the absence of genetic differentiation between the Atlantic and Mediterranean populations and within the Mediterranean basin. The results are in agreement with those previously published using mitochondrial markers. Some considerations on the life history traits of the species are discussed.