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probability of data, lnP(D), is estimated for each model with a given number of clusters.
We applied the admixture model with correlated allelic frequencies (Falush et al. 2003)
as this is the more generai and flexible model (Francois et al. 20 l 0). For each value of
K, ranging from one to the maximum number of populations plus three, l Oindependent
runs were performed, each consisting of l 00000 iterations after a burn-in period of
l 00000, in order to assess consistency of results across runs. All analyses were
performed on the Bioportal server at the University of Osio (Kumar and Skjaeveland
2009). To identify clusters of individuals which might reflect sharp discontinuities in
gene frequencies (Garnier et al. 2004), we considered: l) the average value oflnP(D), 2)
the consistency of results across replicated runs fora given K, and 3) the method
described in Evanno et al. (2005) which retrieves the highest hierarchical structure
present in the data.
The software CLUMPP 1.1.2 (Jakobsson & Rosenberg 2007) was used to check the
consistency ofresults across replicate runs. The average pairwise similarity (H) among
replicate runs for a given K was estimated by a Greedy search algorithrn with l O' 000
random input orders. Replicate runs with similarity values above 0.85, which
corresponds to a similar population structure (Rosenberg et al. 2002), were then merged
to obtain the average membership of all individuals to each cluster. The results were
displayed by the software DISTRUCT 1.1 (Rosenberg 2004).

Genetic structuring was also investigated by a hierarchical analysis of molecular
variance (AMOVA) using the approach described in Excoffier et al. (1992) and
implemented in the software package ARLEQUIN 3.52 (Excoffier & Lischer 2010).
The method partition the total variance into covariance components corresponding to
differences within populations, between populations, between populations within
groups and among groups. First, we performed a two leve) AMOVA analysis to assess

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Gìan Luca Dedola: ANALISI DELLA VARIABILITÀ GENETICA DI PATELLA FéRRUGINEA, PATEL-LA ULl'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