Malacological survey in a bottle of water: a comparative study between manual sampling and environmental DNA metabarcoding approaches.
To assess the effect of anthropogenic activities on ecosystems, it is of prime importance to develop new tools enabling a rapid characterization of ecological communities. Freshwater ecosystems are particularly impacted and threatened by human activities and need thorough attention to preserve their biodiversity and the ecological services they provide. Studying such ecosystems is generally difficult because the associated organisms are hard to sample and to monitor. We present a ready-to-use environmental metabarcoding protocol to characterize and monitor the freshwater gastropods communities from water samples. The efficiency of this new tool was compared to a classical malacological survey at 19 sampled sites from 10 distinct rivers distributed over Corsica Island (France). From a single water sample, our eDNA monitoring tool provided a faithful characterization of the local malacofauna compared to the results obtained from the classical malacological survey, with 97.1% of species detection confirmed by both methods. The present tool successfully detected the 11 freshwater snail species previously reported in Corsica by malacological survey but was limited at the genus level for some species. Moreover, our malacological survey allowed an update of the local distribution of a wide diversity of freshwater snails including invasive species (i.e. Potamopyrgus antipodarum and Physa acuta) as well as snail hosts of pathogens of medical and veterinary importance (i.e. Bulinus truncatus and Galba truncatula). These results strengthened a previous hypothesis of an eventual competitive interaction between B. truncatus and P. antipodarum that could limit the endemization of the uro-genital bilharziasis in Corsica.