The invasive Manila clam Ruditapes philippinarum (Adams and Reeve, 1850) in Northern Adriatic Sea: population genetics assessed by an integrated molecular approach.

The coastal lagoons of the Northern Adriatic Sea are among the most worldwide productive locations of Manila clam Ruditapes philippinarum. Although introduced in Italy in 1983 from the IndoPacific, fishing and exploitation of Manila clam improved during the years as Italy became the leading country in Europe for production of this shellfish. Despite its commercial importance, genetic structure of R. philippinarum in Northern Adriatic Sea has not been previously investigated. Here we present the first genetic study on Manila clam populations inhabiting a Mediterranean area, assessed by both mitochondrial (16S rDNA) and nuclear DNA (microsatellite loci). Our study showed that this species has a limited genetic differentiation at the mitochondrial level, but a higher rate of genetic diversity can be identified by polymorphic markers as microsatellites. In particular, out of 28 alleles, 7 private ones were recorded for the Venice Lagoon populations, 2 for those of Scardovari and one for the Po River Delta populations. These molecular markers suggest the occurrence of at least two different introduction events from different recruitment stocks, representing a powerful tool not only to assess genetic diversity of an introduced species, but also helpful information to manage aquaculture and fishery stocks, and to warrant food quality, safety and for the authentication of shellfish products, and traceabilty path.