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3. RESULTS
Screening 294 specimens of R. philippinarum yielded a total of 87 alleles (see the
Appendix), resulting in 286 unique individuai multilocus genotypes (representing
approximately 97% ofthe specimens).
A PCoA plot ofthe first two principal coordinates (77% oftotal genetic variation) did
not show a clear separation between the Adriatic and Sardinian samples (Fig. 2).
However, the ordination of samples from the Gulf of Olbia along the first principal
coordinate appeared to confirm their geographic position (Fig. 1).
Nevertheless, the highest posterior probability of the data was obtained using the model
w ith K = l , which was retrieved by STRUCTURE (Table 2), supporting the lack of
genetic structuring both within the Gulf of Olbia and between samples from the Gulf of
Olbia and the Lagoon of Sacca di Goro. Similar results were obtained using AMOVA
(DST= 0.004, P > 0.05). Exact tests of population differentiation did not demonstrate
divergence i) among sampl ing sites within the Gulf of Olbia, and ii) between these
samples and the Adriatic sample (pairwise RsTvalues are given in Table 3).
After pooling the Sardinian samples (SPOOL), we found that the allele frequencies
were very similar to the Adriatic population (SGR) (Appendix, Fig. 3). Although
population-specific alleles (private alleles) were present in both populations ( 18 and l O
in SPOOL and SGR, respectively), they occurred at very low frequencies, and 20 out of
28 alleles were found in a single individuai. Alleles 165 and 177 at Asaril6, the private
alleles with the highest frequency, were found in seven and six specimens in SPOOL,
respectively (Appendix, Fig. 3).
Significant deviations from HWE (P < 0.05 after sequential Bonferroni correction for
multiple tests) were found at locus Asari55 in SPOOL and at loci Asari24 and Asari55

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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