[show abstract][hide abstract] ABSTRACT: 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.
[show abstract][hide abstract] ABSTRACT: The reproductive strategy of the simultaneous hermaphrodite Pseudomonocelis paupercula (Platyhelminthes: Proseriata) was investigated using multiple approaches including breeding experiments, anatomical reconstruc-tion, and parentage analysis of offspring. The 18 allozyme loci tested were monomorphic. Conversely, the ISSR markers showed differences among the populations, and allowed us to ascertain whether the offspring were derived from selfing or cross-breeding. The results suggest that selfing is the most common mode of reproduc-tion in this species, with only 8% of the offspring resulting from cross-reproduction. Age at first reproduction of selfers does not differ from that of paired, potentially cross-breeding, specimens. The presence of sperm in the female ducts of individuals that have been isolated since birth suggests the existence of a connection between the male and female reproductive systems that allows self-fertilization. Habitat is suggested to be the key factor shaping the reproductive strategy of the species. P. paupercula is found in highly fragmented brackish-water microhabitats, and selfing may allow for colonization of new habitats that can start from single, unfertilized specimens.
Journal of Experimental Marine Biology and Ecology. 07/2012; 428.
[show abstract][hide abstract] ABSTRACT: Patella ulyssiponensis s.l. is widely distributed in the Mediterranean as well as in the north-eastern Atlantic, from southern Norway to north-western Africa, including Macaronesia. Throughout its range, P. ulyssiponensis s.l. shows a high degree of variability in the shape and colour pattern of the shell and in the colour pattern of the foot. In addition, the species demonstrates widely overlapping morphological parameters with the coexisting P. caerulea (in the Mediterranean), P. vulgata (in north-eastern Atlantic) and P. candei (in the Macaronesian islands). Thus P. ulyssiponensis s.l. identification proves to be difficult. So far, method to unequivocally identify uncertain specimens of P. ulyssiponensis s.l. from the coexisting species was using a molecular taxonomy approach based on the Cytochrome c Oxidase subunit I (COI) sequences analysis. The aim of the present study was to identify specific PCR-RFLP (Restriction Fragment Length Polymorphism PCR-based) markers on the COI sequences which could be used as an alternative and fast diagnostic tool for the discrimination of P. ulyssiponensis s.l. from P. caerulea, P. vulgata and P. candei, when the morphology of the coexisting individuals provided equivocal information. First, we sampled 65 Patella spp. and classified these by means of the COI sequencing. Then, we selected the TaqI endonuclease for the specific RFLP reaction, which produced a combination of RFLP electrophoretic bands, allowing an unequivocal identification of the individuals of P. ulyssiponensis s.l.
Italian Journal of Zoology 03/2012; 79(1):50-59. · 0.89 Impact Factor
[show abstract][hide abstract] ABSTRACT: a b s t r a c t The genetic variability of microsatellites was investigated among allochthonous pop-ulations of Ruditapes philippinarum (Bivalvia, Veneridae) at six sites in the Gulf of Olbia (North-East Sardinia) and one site in the Lagoon of Sacca di Goro (North Adriatic Sea). Our results demonstrate the lack of genetic substructuring of R. philippinarum populations within the Gulf of Olbia. Furthermore, we found highly similar estimates of within-population genetic variability without evidence of genetic differentiation between Sardinian and Adriatic populations. The lack of a signature of a founder effect in the Sardinian samples, notwithstanding their recent introduction, indicates that the number of R. philippinarum individuals released into the Gulf of Olbia may have been high enough to reduce the loss of genetic variability due to genetic drift. Furthermore, the absence of genetic differentiation observed between samples from the two areas suggests that the two populations belong to the same gene pool. Our results also indicated that R. philip-pinarum is rapidly colonizing the Gulf of Olbia and the neighboring areas, which is likely favored by its high potential for dispersal.
[show abstract][hide abstract] ABSTRACT: Patella ferruginea Gmelin, 1791 is an endangered marine gastropod endemic to the Western Mediterranean. Its range is restricted to the Sardinian-Corsican region (SCR), North Africa, a few scattered sites in Southern Spain, and Sicily. Inter-simple sequence repeat (ISSR) markers and three different mitochondrial DNA (mtDNA) regions, Cytochrome c Oxidase subunit I, 12S (small-subunit ribosomal RNA gene) and 16S (large-subunit ribosomal RNA gene), were used to investigate the presence of genetic population structuring. The mtDNA sequences showed very low levels of genetic differentiation. Conversely, ISSRs showed the presence of two main genetic groups, corresponding to Spain, North Africa and Sicily and the SCR. The SCR was further split into two subgroups. The ISSR results suggest that, on a regional scale, the genetic structure of P. ferruginea is mainly determined by the restriction of gene flow by dispersal barriers. On a more local scale human harvesting may play a crucial role in population structuring by increasing the effect of genetic drift.
[show abstract][hide abstract] ABSTRACT: We report a sampling strategy based on Mendelian Breeding Units (MBUs), representing an interbreeding group of individuals sharing a common gene pool. The identification of MBUs is crucial for case-control experimental design in association studies. The aim of this work was to evaluate the possible existence of bias in terms of genetic variability and haplogroup frequencies in the MBU sample, due to severe sample selection. In order to reach this goal, the MBU sampling strategy was compared to a standard selection of individuals according to their surname and place of birth. We analysed mitochondrial DNA variation (first hypervariable segment and coding region) in unrelated healthy subjects from two different areas of Sardinia: the area around the town of Cabras and the western Campidano area. No statistically significant differences were observed when the two sampling methods were compared, indicating that the stringent sample selection needed to establish a MBU does not alter original genetic variability and haplogroup distribution. Therefore, the MBU sampling strategy can be considered a useful tool in association studies of complex traits.
Genetics and Molecular Biology 04/2011; 34(2):187-94. · 0.74 Impact Factor
[show abstract][hide abstract] ABSTRACT: Patella ferruginea is an endangered marine gastropod, distributed on the western Mediterranean coasts, whose range has progressively contracted, due to intense human exploitation. A genetic analysis was performed on two unidentified young individuals belonging to the genus Patella found attached to the shell of an adult of P. ferruginea , with a twofold aim: (i) to achieve their correct taxonomic attribution by means of the DNA barcoding; and (ii) to shed some light on the hypothesized larval philopatry and/or juveniles phoresis in P. ferruginea . The survey was carried out comparing the sequences of the cytochrome c oxidase subunit I (COI) Folmer region obtained for the two juveniles with those obtained for adults of P. ferruginea , P. caerulea , P. rustica , and P. ulyssiponensis , from different sites of the western Mediterranean, by means of maximum likelihood cluster analysis and a Bayesian-based assignment test. Results obtained evidenced that: (i) COI may be used with confidence as DNA barcoding in the genus Patella ; and (ii) the two juveniles studied are not conspecific: one belonged to P. ferruginea , the other to P. rustica . The latter finding raises doubts about the juvenile phoresis and about the occurrence of larval philopatry in P. ferruginea , suggesting that an extensive use of a molecular approach for a better evaluation of the recruitment features of this endangered species should be adopted.
Journal of the Marine Biological Association of the UK 01/2010; · 1.02 Impact Factor
[show abstract][hide abstract] ABSTRACT: The ferruginean limpet Patella ferruginea, formerly distributed in Western Mediterranean, is now limited to a few restricted areas, due to intense human exploitation. Its distribution in Northern Sardinia is particularly fragmented, the larger populations being encompassed by Marine Protected Areas (MPAs). In order to plan conservation strategies for this species, we studied the levels of genetic variability within and among populations by means of ISSRs, SSRs and, for phylogeographic purposes, of COI sequences.
ISSRs evidenced a low level of gene flow (FST < 0.02 n.s.) between populations from North-East Sardinia (where two relatively close MPAs are present), whereas populations from North-West Sardinia (with two far apart MPAs) show strong differentiation (FST > 0.31 ***), suggesting that gene flow is relevant only at very small geographic scale. The use of heterologous SSRs developed in the congener P. rustica and P. depressa hints at the possibility that at least some populations are tetraploids. Since in Northern Africa diploid populations only are known, this finding suggests a possible phenomenon of incipient speciation. The issue is being investigated by RT-PCR and karyotype determination after cell culture.
FISV - 11th Annual Congress - Poster1 01/2009; 09/2009