Résumé:
A study of the population genetic structures of the limpet Patella rustica (Linnaeus, 1758) (Gastropoda: Prosobranchia) has been established on the Algerian coast as well as on a spread area between the Mediterranean and the Atlantic. This work was carried out on 167 sequences of the portion of the mitochondrial gene Cytochrome Oxydase I "COI" taken from NCBI (GenBank) belonging to P. rustica and sampled from several stations located between the Mediterranean and the Atlantic including 24 sequences from 7 stations on the Algerian coast [Vieille calle El Kala (VK), Rocher Noir (RN), Ziama Mensouria (ZM), Figuier Plage (FP), Bérard (BE), Cap Ivi (CV) and Stidia (ST)]. In order to find models of population genetic structures of P. rustica well established at the local scale (Algerian coast) and at the enlarged scale (Mediterranean / Atlantic), phylogenetic and phylogeographic analyzes were carried out at the help of several bioinformatics programs (FinchTv, BioEdit, Mega5, NetWork, DnaSp and Arlequin). The results showed that the populations of P. rustica started from a recent expansion due to a bottleneck effect. In addition, 5 new Algerian haplotypes never listed in the NCBI were revealed. The results of the MOlecular Analysis of VAriance (AMOVA) showed that the populations of the east of the Algerian coast (VK, RN, ZM and FP) are well separated from the populations of the west region (ST, CV and BE) . The extended phylogeographic study has shown that the Siculo-Tunisian Strait is the limit between the populations of the eastern Mediterranean and the populations of the western Mediterranean as well as the Atlantic. Finally, it seems that the frontal currents are the cause of this divergence creating an invisible barrier between the different populations of P. rustica.
