Unexpected and spatially structured genetic diversity of the relict population of the endangered corsican land snail Tyrrhenaria ceratina

We thank all the volunteers who realized the sample collection, especially the team of the Centre Permanent d’Initiatives pour l’Environnement d’Ajaccio mobilized for the project “Aio lumacchi, Allez les escargots” funded by Office Français de la Biodiversité and the wardens of the Collectivité Territoriale de Corse. We also thank DREAL Corse for funding support. Handling and sampling of this protected species were performed under permits: Arrêtés préfectoraux 2 A 2018-01-29-001, 2 A 2020-03-25-001 and 2 A-2021-02-25-003.; International audience; Population genetics of threatened species provides information about evolutionary pressures over those populations and thus may inform conservation management strategies. However, conservation genetics still has a low impact on conservation practices. This study's aim is to integrate genetics in the conservation management of the only-known population of an extremely narrow-range endemic Corsican snail-Tyrrhenaria ceratina-, whose distribution area is restricted to the Ricantu site in Corsica. Using non-invasive DNA samples of 210 individuals, we amplified 13 microsatellites loci to assess the population viability, genetic structure and demographic history of the population, along with the estimation of the historical and contemporary gene flow between identified genetic clusters. We also estimated the dispersal ability of the species. Our results showed a surprisingly high genetic diversity, along with a pattern of isolation by distance (IBD) and a strongly spatialized genetic structure. Furthermore, we underlined a low functional connectivity, along with evidence of a recent decline in the population size, which are both likely due to a historical fragmentation between the sampled areas, caused by anthropization. Overall, this study allows to provide a first insight about the functioning of the population, to guide future conservation actions for the species.