Phylogeographical analysis of Paracentrotus lividus was carried out by means of sequencing the mitochondrial cytochrome b gene (1143 bp) of 260 individuals collected at 22 Mediterranean and four Atlantic localities. Against a background of high haplotype diversity and shallow genetic structuring, we observed significant genetic divergence between the Adriatic Sea and the rest of the Mediterranean, as well as between the Mediterranean and the Atlantic sample groups. Furthermore, on the largest spatial scale, isolation by distance was detected. Three main haplogroups were identified by network and Bayesian assignment analyses. The relative proportions of haplogroups were different in the four regions considered, with the exception of Western and Eastern Mediterranean that showed a similar pattern. This result together with the outcome of Snn statistics, analysis of molecular variance and network analyses allowed to identify three weakly differentiated populations corresponding to the Atlantic, Western + Eastern Mediterranean, and Adriatic seas. Analyses of mismatch distribution and neutrality tests were consistent with the presence of genetic structuring and past demographic expansion(s). From a fisheries perspective, the results obtained in the present study are consistent with genetic sustainability of current exploitation; local depleted stocks are recurrently replenished by recruits that may have originated from nonharvested areas.
Samples of the brackish-water cyprinodontid fish Aphanius fasciatus from 11 Medterranean coastal brackish-water habitats were examined for variation at 43 allozyme loci. Sixteen loci were polymorphic in at least 1 population. Estimates of genetic variability revealed low levels of polymorphism, with mean effective number of alleles per locus ranging from 1.02 (SE 0.01) to 1.10 (SE 0.04) and average expected heterozygosity values from 0.013 (SE 0.007) to 0.062 (SE 0.022). The mean Weir & Cockerham f = 0.060 (SE 0.019) confirmed the general concordance with Hardy-Weinberg equilibrium within populations assessed by exact tests. The presence of various private alleles and the mean value of the coancestry coefficient, 0 -0.507 (SE 0.078), indicated a marked genetic dvergence among populations. Nei's genetic distance values were characteristic of populations within species, ranging from 0.001 (SE 0.000) to 0.098 (SE 0.044). Genetic affinities obtained by UPGMA cluster analysis were consistent with the geographical distribution of populations. The h g h degree of genetic divergence among A. fasciatus populations corresponds to the naturally fragmented distribution of the species and to restricted gene flow between populations, due to the limited dispersal potential of the species. Furthermore, genetic and geographical distances between populations are consistent with the prediction that the species is genetically structured by isolation by distance.
Pinna nobilis is the largest endemic Mediterranean marine bivalve. During past centuries, various human activities have promoted the regression of its populations. As a consequence of stringent standards of protection, demographic expansions are currently reported in many sites. The aim of this study was to provide the first large broad-scale insight into the genetic variability of P. nobilis in the area that encompasses the western Mediterranean, Ionian Sea, and Adriatic Sea marine ecoregions. To accomplish this objective twenty-five populations from this area were surveyed using two mitochondrial DNA markers (COI and 16S). Our dataset was then merged with those obtained in other studies for the Aegean and Tunisian populations (eastern Mediterranean), and statistical analyses (Bayesian model-based clustering, median-joining network, AMOVA, mismatch distribution, Tajima’s and Fu’s neutrality tests and Bayesian skyline plots) were performed. The results revealed genetic divergence among three distinguishable areas: (1) western Mediterranean and Ionian Sea; (2) Adriatic Sea; and (3) Aegean Sea and Tunisian coastal areas. From a conservational point of view, populations from the three genetically divergent groups found may be considered as different management units.
The blue and red shrimp Aristeus antenantus supports an important commercial fishery in the Western Mediterranean, adjacent Atlantic waters and Mozambique Channel (western Indian Ocean). This study investigates its genetic structure by examining a total of 506 individuals from Mediterranean, Atlantic and Indian Ocean locations. In order to identify putative genetic stocks, sequences from 16S rDNA (546 bp) and COI (514 bp) genes were used. Genetic diversity, estimated by haplotypic and nucleotidic diversity, was lower in the Western Mediterranean than in samples from other locations. The high haplotypic diversity of the Eastern Mediterranean, Atlantic and Indian Ocean samples reflects the occurrence of a number of private haplotypes, which are also responsible for significant genetic divergence between these samples and the Western Mediterranean ones. The analysis of mismatch distributions, neutrality tests, and star-like patterns present in the network of haplotypes provided consistent inference of past population expansion in the Western Mediterranean, Atlantic and Mozambique Channel regions. Our study provides the first evidence of genetic structuring in A. antennatus across its distributional range.KEY WORDS: Aristeus antennatus · COI · 16S rDNA · Genetic structure · Atlantic Ocean · Mediterranean Sea · Western Indian Ocean Resale or republication not permitted without written consent of the publisherMar Ecol Prog Ser 421: [163][164][165][166][167][168][169][170][171] 2011 roboration of Atlantic-Mediterranean differentiation has been provided by multiple examples of the population structure of marine species, from pioneer work on crustaceans (Chthamalus montagui, Dando & Southward 1981), mollusks (Mytilus galloprovincialis, Quesada et al. 1995a,b; Sepia officinalis, Pérez-Losada et al. 1999) and fishes (Platichthys flesus, Borsa et al. 1997; Merluccius merluccius, Roldán et al. 1998) down to the present day.The blue and red shrimp Aristeus antennatus (Risso, 1816) is an important commercial deep-sea species that inhabits the Mediterranean, northeast Atlantic waters from Portugal to the Cape Verde Islands (Holthuis 1980), and the Indian Ocean from the Maldive Islands to Zanzibar, Mozambique and South Africa (Freitas 1985). In recent years, it has also been recorded off the northern coasts of Brazil (Serejo et al. 2007). A. antennatus is a eurybathic species ranging from 80 to 3300 m depth, with peaks of abundance at 600 to 900 m depth (Campillo 1994, Sardà et al. 2004). Its abundance is also geographically variable, with density in the Western Mediterranean being higher than that in the eastern basin ). Significant morphological differences have been observed in individuals from the 2 basins. However, no allozyme divergence was found (Sardà et al. 1998) and the differences were explained as being a response to hydrological and ecological characteristics of the 2 Mediterranean basins (Sarà 1985). Recently, new molecular markers (microsatellites, Cannas et al. 2008; mitochondrial control region, ...
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