Unraveling the complexity of Corbicula clams invasion in Lake Garda (Italy)

Lake Garda, the largest Italian lake, is suffering from the introduction of several non-indigenous species during the last decades and can now be considered one of the main European freshwater hotspots of xenodiversity. Among the Bivalvia (Veneroidea, Cyrenidae), Corbicula fluminea and Corbicula fluminalis were first recorded in 2002 and 2008 respectively, and are now widespread in the southern part of the basin. Recent observation of specimens that did not resemble either of these taxa, suggested that the populations of invasive Corbicula of Lake Garda could include some other taxa not previously recorded. With this aim, a thoroughly characterization of Corbicula shells found at Lake Garda was made. By studying morphometric parameters and comparing them with specimens collected in Spain (Ebro and Ter rivers), the presence in Lake Garda of two other related species not previously recorded in Italy, namely C. leana and C. largillierti, has been confirmed. The syntopic presence of at least four species of this genus in a single environment is a singular occurrence both in Italy and Europe.