Hybridation naturelle entre les deux sous-espèces d'huîtres creuses Crassostrea gigas et Crassostrea angulata au sud de l'Europe

Crassostrea angulata and Crassostrea gigas, two cupped oysters of Asian origin (O'Foighil et al, 1998), have been introduced successively in Europe during the XVlth and the XXth century (Grizel et Héral, 1991). The present populations of C. angulata appear to be limited to the south of Spain and Portugal, whereas the distribution of C. gigas in Europe is rising because of the development of oyster farming. The distinction between the two subspecies in based on a RFLP marker of the mitochondrial genome (COI) which shows a strong genetic differentiation between the two subspecies populations (Boudry et al., 1998). On the contrary, the nuclear markers (microsatellites) showed a smaller genetic differentiation between them (Huvet et al, under press). The absence of a reproductive barrier between C. angulata and C. gigas, which has been demonstrated experimentally (Gaffney and Allen, 1993; Huvet, 2000), leads us to suspect some hybridization phenomenons between these two cupped oysters in the wild. In order to study these phenomenons, 9 populations have been sampled along the European Atlantic coast (France, Spain, Portugal).