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Genetic structure was also investigated with an individual-based approach (Mank and
Avise, 2004). Genetic substructuring was inferred by the Bayesian model-based
clustering algorithm that is included in the STRUCTURE 2.2.3 software (Pritchard et
al. , 2000), applying the admixture model with correlated allelic frequencies (Falush et
al. , 2003). The most likely population structure was inferred from multilocus individuai
genotypes by estimating the posterior probability ofthe data (PPD) according to
Pritchard and Wen (2004) and, if necessary, the consistency of results across runs. For
each value ofK (the number of assumed genetic clusters), l Oindependent runs were
performed, each consisting of l 00,000 iterations after a bum-in period of l 00,000.
Furthermore, the partitioning of genetic variation within and among sampling sites was
estimated by AMOVA (Analysis ofMolecular Variance) using ARLEQUIN 3.52
software (Excoffier and Lischer, 20 l 0). The significance of genetic differentiation was
tested by a permutation test (10,000 replicates). Overall DsTwas calculated followed by
a pairwise computation of RsT values (Siatkin, 1995) between all pairs of sampling sites
within the Gulf of Olbia and the Adriatic sample. The significance of the random
distribution of individuals among sampling sites was evaluated with exact tests that are
analogous to Fisher's contingency tables (Raymond and Rousset, 1995). We defined
two populations from subsequent genetic analyses based upon the results of genetic
structuring: one population was obtained by pooling the samples from the Gulf of Olbia
(SPOOL), and the other population represented the sample from the Lagoon of Sacca di
Goro (SGR).
Conformity to Hardy-Weinberg equilibrium (HWE) and linkage disequilibrium (LD)
were tested with the Markov chain randomization test (Guo and Thompson, 1992) using
GENEPOP 4.0 (Rousset, 2008). Whenever necessary, the sequential Bonferroni

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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