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Regardless of the source of Sardinian sarnples, the number of individuals of R.
philippinarum that were scattered in the Gulf of Olbia rnay have been high enough to
avoid the consequence of a founder effect. Indeed, the higher fecundity rates that
invasive or introduced species exhibit in new environrnents (i.a. Grosholz and Ruiz,
2003) often overcome the Ioss of genetic diversity that is caused by genetic bottlenecks
or the founder effect (Andreakis et al., 2009). In this context, R. philippinarum may be
considered a 'good invader' species due to its effective larva) dispersa) and high rate of
reproduction. Cannas et al. (2009) reported the occurrence of R. philippinarum recruits
one year after their first recorded release in the Gulf of Olbia.
Interestingly, Delgado and Perez-Carnacho (2007) bave reported that under the sarne
experirnental conditions, R. philippinarum dernonstrates superior reproductive
performance when cornpared to R. decussatus. This trait, coupled with high levels of
genetic diversity, may allow R. philippinarum to quickly adapt to the new
environmental conditions (see Estoup and Guillemaud, 2010, and the references
therein).
The previously recorded hybridization between R. philippinarum and R. decussatus
(Hurtado et al. , 201 1) represents a further threat, because hybridization may enhance the
invasiveness of an allochthonous species by producing novel genotypes that better adapt
to Iocal conditions (see Henry et al. , 2009, and the references therein).
These factors raise concems about the conservation and management of the
autochthonous R. decussatus, whose populations may suffer from competition with R.
philippinarum (Chessa et al., 2005) as well as the rnaladaptation that occurs as a result
ofhybridization between the two species (Hurtado et al. , 2011). Finally, the recent
introduction of R. philippinarum in Sardinia presents the opportunity to follow the

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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 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