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correction was applied toP values to avoid type I errors that can occur due to multiple
testing (Hochberg, 1988).
Estimates of genetic variability were computed using the GENALEX software. The
number and size range of alleles, allelic frequencies, observed (H0) and expected (He)
heterozygosity, and inbreeding coefficient (F1s) values were estimated at each
microsatellite locus. Moreover, the mean number of alleies (Na), the number of
effective alleles (Ne), and the observed (H0) and expected (He) heterozygosity were also
calculated for the loci of each inferred population (SPOOL and SGR).
The statistica! significance for differences in the expected heterozygosity was tested
w ith a Wilcoxon rank-sum test, using the R 2.11.1 package (R Development Core
Team, 2010).
The possibility of a founder effect due to recent colonization or expansions in SPOOL
and SGR was tested using the software BOTTLENECK 1.2.02 (Comuet and Luikart,
1996+; Piry et al., 1999). Indeed, after genetic bottlenecks, the number of alleies
reduced faster than heterozygosity, leading to excess of gene diversity when compared
to a mutation-drift equilibrium. Conversely, an expanding population accumulates new
alleles at a high rate, wbicb contribute little to beterozygosity because of their low
frequency, resulting in a gene diversity that was lower than expected at mutation-drift
equilibrium (Luikart et al., 1998). Because the expected heterozygosity is highly
dependent on the selected mode! of microsatellite evolution (Hawley et al., 2006), the
analysis was performed using both the strict stepwise mutation mode! (SMM) and the
two-phase mutation mode! (TPM) (see Cornuet and Luikart, 1996). Here, the reported
results are based on simulations with a TPM mode! set at 95% and the infinite allele
mode! at 5%. The significance ofthe tests was assessed using Wilcoxon rank-sum test,

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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 MOLECOLARl 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