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partitioning proposed by Bianchi and Morri (2000), involved in geologica), climatic and
hydrologic factors,
The placing the group (SES), including populations from Sardinia, Elba Island and
Sicily, corresponds to the bio-geographic Mediterranean sector "Balearic Sea to
Tyrrhenian Sea" identified by Bianchi and Morri (2000). It is not surprising that Sicilian
southem populations (PAC and OGN) are here included, being Sicily located westward
of the boundary between the western and eastern Mediterranean according not only to
Bianchi and Morri (2000) but also to Pérès and Picard (1964).

The centre of variability expansion in the Tyrrhenian Sea is located in
correspondence of the North-East of Sardinia. It is an interesting finding, that
corroborates the theory of island biogeography (MacArthur and Wilson 1967)
suggesting that a large extension of marine protected areas (MPA) could represent a
source of biodiversity for neighbouring areas. In fact along north-eastem Sardinian
coast two MPAs (Parco Nazionale Arcipelago di La Maddalena and Area Marina
Protetta Tavolara Capo Coda Cavallo), which could be involved in the high variability
occurring in the area, are situated. Mismatch analysis and neutrality test values support
the hypothesis of a recently originated population, which probably tends to the
equilibrium (Rogers and Harpending 1992).

Grecian and Tunisian samples (group GT) represent part of the genetic
variability of eastem Mediterranean corresponding to the bio-geographic sectors "Gulf
of Gabès to Levant Sea" and ''North Aegean" identified by Bianchi and Morri (2000).
Samples from northern Tunisia (N) are included in this group being molecularly similar
to the other Tunisian populations analysed. Anyway it is not surprising since two
studies on within-Mediterranean distributions of sponges (Pansini and Longo, 2003) and
pycnogonids (Chimenz-Gusso and Lattanzi, 2003) found higher fauna! affinities

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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