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between eastem and south-westem Mediterranean Iocalities than between north-westem
and south-westem localities.

Furtherrnore, a recent study carried out on the black-striped pipefish Syngnathus
abaster (Syngnatidae), which lives in brackish-water habitats and presents reduced
potential for dispersa), evidenced a sharp genetic structuring between Tunisian and
French populations (Ben Alaya et al. , 20 11). Sample from Cyprus, which should be part
of the eastem Mediterranean bio-geographic sector "Ionian Sea and South Aegean"
identified by Bianchi and Morri, did not show any similarity with Grecian and Tunisian
populations, rather it shares haplotypes with populations from Sardinia, Elba Island,
Sicily and Venetian Lagoon. Anyway the reduced size of Cyprian sample (two
individuals only) did not allow to conclusively infer on these results.

Grecian and Tunisian group (GT) shows two centres of expansion, which
correspond to the occurrence of two different bio-geographic sectors within it (Bianchi
and Morri , 2000). Anyway, demographic analysis carried out on the whole sample
strongly evidenced the occurrence of a homogeneous population in demographic
expansion. Such finding represents a possible consequence of phenomena of bottle-neck
followed by founder effects as it is suggested by the high rate of haplotype sharing
between Grecian and Tunisian populations.

Venetian lagoon (VL) is characterized by the occurrence of an isolated
population which although showing a moderate haplotype sharing with SES group,
statistically diverges from the other two Mediterranean groups identified (SES and GT).
This area corresponds to the bio-geographic Mediterranean sector "North Adriatic"
described by Bianchi and Morri. Mismatch analysis and neutrality tests advance the
trend of this population to the equilibrium suggesting that it may be evolving
independently from others. The occurrence in the Venetian Lagoon of haplotypes

66

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