Mitochondrial DNA Reveals Genetic Structuring of Pinna nobilis across the Mediterranean Sea

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.

Highly polymorphic microsatellite markers for the Mediterranean endemic fan mussel Pinna nobilis

“…The fan mussel Pinna nobilis (Linnaeus 1758) (Mollusca: Bivalvia) is an endemic Mediterranean species with great conservation interest due to regression of its populations as a consequence of overexploitation and habitat deterioration (Rabaoui et al, 2011;Sanna et al, 2013). It has been recognized as an endangered species in the Mediterranean Sea according to European Council Directive 92/43/EEC and is under strict protection (Annex IV of the directive); its capture is forbidden (92/43/EEC).…”

“…P. nobilis presents veliger-stage larvae, which drift in the water column for 5-10 days before settling in the sediment, showing highly variable recruitment rates (Hendriks et al, 2012). Despite its endangered conservation status, few studies have addressed population genetics and connectivity patterns in P. nobilis (Katsares et al, 2008;Rabaoui et al, 2011;Sanna et al, 2013;. These studies have used 2 mitochondrial (COI and 16S genes) and 2 nuclear (18S and 28S) markers, which were limited in their resolution to assess the current genetic structure of P. nobilis populations.…”

The Pen Shell, Pinna nobilis

“…Knowledge of the amount of genetic variability and distribution in space and time is therefore crucial for a correct diagnosis of the conservation status and viability of populations and the threats to their survival (Escudero et al, 2003;Frankham, 1995). There are few studies assessing the population genetics and connectivity patterns of P. nobilis (but see Katsares et al, 2008;Rabaoui et al, 2011;Sanna et al, 2011Sanna et al, , 2013Sanna et al, , 2014. These studies used two mitochondrial (cytochrome c oxidase subunit I, COI and 16S genes) and two nuclear (18S and 28S) markers.…”

“…Therefore, mtDNA COI sequences have not provided evidence for a differentiation pattern among Tunisian coastline populations. Hence, P. nobilis populations are thought to be structured in two large, homogeneous groups of populations, one spanning two Mediterranean marine ecoregions (the western Mediterranean and Ionian Sea), which genetically diverges from the other, consisting of the Adriatic subpopulation and those from the Aegean Sea and Tunisian coasts (eastern Mediterranean; Sanna et al, 2013). New specific primers for COI (see Table 2) showed a genetic discontinuity between P. nobilis from the Adriatic Sea and those from the rest of the Mediterranean Sea, which may result from the semi-enclosed nature of the Adriatic Sea, which represents a well-defined phylogeographic region within the Mediterranean (Patarnello et al, 2007).…”

“…In addition to their peculiar geographic position, samples from Adriatic Venetian Lagoon are considered "peripheral isolate" (Frey, 1993). The presence of only one point mutation separating the Aegean and Tunisian samples from those from Sardinia, Corsica, Elba Island, Sicily and the Venetian Lagoon, evidenced a common origin of P. nobilis populations in the Mediterranean Sea (Sanna et al, 2013). The low genetic variability among populations suggests that pelagic larval dispersion of the species, which is influenced by hydrogeography, leads to high gene flow and high connectivity among populations (Katsares et al, 2008).…”