Page 129 - Dedola2011

Introduction
The limpet Patella ulyssiponensis Gmelin, 1791 (Mollusca: Gastropoda) is distributed
in the shallow subtidal and low intertidal zones where it can be found on the more
exposed shores as well as in mid-shore rock pools (Guerra and Gaudencio 1986;
Hawkins et al. 1990). The species is one ofthe most widely distributed limpets, though
the assessment of its distribution range has been hampered by two factors. First, the
identification of P. ulyssiponensis is difficult because ofthe broadly overlapping
morphological variability with the other Patella species living in the lower part of
intertidal zone. For instance, in severa! Mediterranean localities P. ulyssiponensis may
not be safely distinguished by the endemie Patella caerulea Linnaeus, 1758. Indeed, the
shell and foot colour pattern as well as the shell shape may not allow to unequivocally
discriminate between the two species (Cretella et al. 1990; Sella et al. 1993; Mauro et
al. 2003; Casu et al. 2010). Similarly, along the Atlantic European coasts the distinction
between P. ulyssiponensis s.I. and Patella vulgata Linnaeus, 1758, may be equally
troublesome (i.a. , Cabrai 2003; Pagarete 2005). Furthermore, the picture has been
complicated by the fact that, based upon the extremely variable shell sculpture and
colour P. ulyssiponensis was described as a complex of subspecies (Christiaens 1973).
Only recently, the use ofmolecular tools allowed both a better resolution ofthe
relationships within the P. ulyssiponensis complex (Weber and Hawkins 2005; Sa Pinto
et al. 2005, 2008) and a more accurate identification ofthe species with respect to its
congeners (Sanna et al. 2011 in press). The high leve! of genetic differentiation
evidenced by allozymes between populations from the Mediterranean and the European
continental shoreline of the Atlantic, and those from the Macaronesian islands, led
Weber and Hawkins (2005) to hypothesise the presence oftwo distinct species: P.
ulyssiponensis from the European continental coasts, and Patella aspera R6ding, 1798

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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