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4. Discussion
The problem of a correct attribution of Patella individuals may be relevant in the
ecological and biodiversity studies. Indeed, it regards not only single puzzling specimens
within a population, but entire populations as well. For instance, during a study on P.
caerulea and P. ulyssiponensis along the Sicilian coasts, Mauro et al. (2003) noted that, at
Capo Gallo, it was not possible to identify any specimens ofthe two Patella species, based
on the morphological features.
Accordingly, we observed that some populations from our Mediterranean sampling sites
(as in Insel Cres, Molarotto Island, and Ceuta harbour; see Table II for details) are
composed almost entirely by specimens of P. ulyssiponensis and P. caerulea with
overlapping morphology.
Similar difficulties occurred for all the Patella specimens from Las Galletas (Tenerife) as
well as for some specimens from Fort du Dellec (Brittany). Noteworthy, the preliminary
tentative attribution of sampled individuals toP. ulyssiponensis s.i., based on shell
morphology and external foot colour, led to deceptive results (Table II).
An instance ofthe high morphological similarity between the shells of P. uiyssiponesis s.i.
and those ofthe sympatric species P. caerulea (in Mediterranean), P. vulgata (in the
Atlantic continental coasts) and P. candei species complex (in Macaronesia) is reported in
Figure 4b.
It should be noted that P. ulyssiponensis s.i. individuals are more similar to the congenerics
from the same geographical area (pairs 1-2, 3-4, 5-6) in comparison to individuals from
different localities (specimens 1-3-5).
The wide morphological variation, with the overlapping morphology and colour displayed
by P. uiyssiponensis s. l. and some congenerics occurring in the intertidal, is presumably
promoted by the habitat heterogeneity which characterises the zone, with differences in

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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