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found a North-East decreasing gradient of genetic variability arnong populations that
was explained in the light of the variance in hydrographic pararneters of the area
analysed. No evidence of rnolecular divergence was found between the two
rnorphological forms.
Starting frorn such studies, increasing the researchers' efforts in irnproving rnolecular
analysis on the P. nobilis populations could be helpful to better clarify how
environrnental pararneters and anthropogenic stress could have acted on the population
dynarnics of this species together with stochastic forces such as founder effects or
genetic bottlenecks.

Up two decades ago the populations of P. nobilis throughout the whole
Mediterranean have been endangered by the reduction of their natural habitat as rnain
consequence of marine pollution and hurnan activities principally involved in
recreational and commerciai fishing (Vincente, 1990; Zavodnik et al. , 1991; Vicente
and Moreteau, 1991; Richardson et al. , 2004; Rabaoui et al. , 2010).

In order to cope with the decreasing population density of this species, in 1995
P. nobilis has been included in the list of Mediterranean endangered species (Annex IV
of the Habitat Directive and Annex II of the Barcelona Convention).

In sueh context, the airn of this work is to provide the first insight on genetic
variability and phylogeographic patterns characterizing populations of P. nobilis from
both western and eastern Mediterranean areas. Furthermore, since bivalve's fecundity
usually increases with size and age (Gosling, 2003) with irnportant irnplications on
recruitrnent effect, a specific non-lethal sarnpling rnethod was developed in order to
collect sarnples without killing individuals which can live for over 20 years (Richardson
et al., 1999; Siletié and Peharda, 2003; Richardson et al., 2004). Mitochondrial rnarkers

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Gìan Luca Dedola: ANALISI DELLA VARIABILITÀ GENETICA DI PATELLA FéRRUGINEA, PATEL.LA UL l'SSIPONENSIS (MOLLUSCA: GASTROPODA) E PINNA
NOBILIS (MOLLUSCA: BIVALVIA): lLCONTRJBUTO DEl DATI MOLECOLARI ALLA CONSERVAZIONE DI SPECIE MINACCIATE · Tesi di douorato in Scienze
della natura e delle sue risorse • indiri7.zo BK>logi.a Ambientale, Università degli Studi di Sassarl