Assessment of the distribution of Ruditapes spp. in northern Mediterranean sites using morphological and genetic data

Abstract

ABSTRACT In the 1970s, Ruditapes philippinarum was introduced to France at Arcachon Bay for aquaculture. At present, in Europe, R. philippinarum is often found in place of the native species Ruditapes decussatus. The aim of this study is to evaluate the distribution of these two species along the northern Mediterranean coastline using morphological and morphometric analysis. The sampling period was between June and December 2018. Among the 11 French sites, only 2 contained R. philippinarum, whereas only the indigenous species was present at the other sites. Genetic analyses were used to confirm species identity and to confirm this distribution. A site in Italy, Pialassa Baiona, was also added to the sample. This analysis of Ruditapes from multiple French sites and one Italian site highlights species-level differences in shell morphology between R. decussatus and R. philippinarum. The intraspecific morphometric analysis showed the presence of different groups depending on spatial scales (i.e. at the large scale, between the Mediterranean Sea and the Atlantic, and on the small scale, that is within the Berre lagoon in France. No relationship between morphometric and genetic variation was found. This suggests that the differences in the shell shape of Ruditapes are driven by local environmental conditions.