COI sequencing as tool for the taxonomic attribution of Patella spp. (Gastropoda): the case of morphologically undistinguishable juveniles settled on a Patella ferruginea adult

Patella ferruginea is an endangered marine gastropod, distributed on the western Mediterranean coasts, whose range has progressively contracted, due to intense human exploitation. A genetic analysis was performed on two unidentified young individuals belonging to the genus Patella found attached to the shell of an adult of P. ferruginea, with a twofold aim: (i) to achieve their correct taxonomic attribution by means of the DNA barcoding; and (ii) to shed some light on the hypothesized larval philopatry and/or juveniles phoresis in P. ferruginea. The survey was carried out comparing the sequences of the cytochrome c oxidase subunit I (COI) Folmer region obtained for the two juveniles with those obtained for adults of P. ferruginea, P. caerulea, P. rustica, and P. ulyssiponensis, from different sites of the western Mediterranean, by means of maximum likelihood cluster analysis and a Bayesian-based assignment test. Results obtained evidenced that: (i) COI may be used with confidence as DNA barcoding in the genus Patella; and (ii) the two juveniles studied are not conspecific: one belonged to P. ferruginea, the other to P. rustica. The latter finding raises doubts about the juvenile phoresis and about the occurrence of larval philopatry in P. ferruginea, suggesting that an extensive use of a molecular approach for a better evaluation of the recruitment features of this endangered species should be adopted.