The invasion of Obama nungara (Platyhelminthes: Geoplanidae) in metropolitan France and its impact on earthworm communities.

International audience

anglais. Obama nungara (Platyhelminthes: Geoplanidae) is a terrestrial flatworm native to South Americaand considered invasive in France, with a reported presence in three quarters of France. To date, it has onlybeen recorded in anthropized habitats such as private gardens. This species is a known predator ofearthworms which play an essential role in soil ecosystems, for instance through decomposition of organicmatter and by digging galleries ensuring soil aeration. In temperate areas, earthworm species may beroughly classified in three ecotypes (i.e. epigeic, anecic and endogeic) that may have various impacts onsoil properties. Because anecic and epigeic earthworms spend time on the soil surface, it is assumed that O.nungara predation could impact these ecotypes more than endogeic earthworms, thus impacting native soilecosystems.The present study is part of a project that aims to understand the impact of O. nungara on earthwormcommunities and on soil functioning. Here, our main objective was to describe the dynamics of O. nungarapopulations in introduced sites of metropolitan France, in relation to the structure of earthwormcommunities. Thus, we monitored twice a year (Autumn and Spring) the abundance of O. nungara, theabundance of earthworms and their community structure, in 10 different sites (private gardens, greenhouseand vegetalized roof) across France, from 2021 to 2023.In addition, we analyzed daily monitoring data obtained in one of the gardens by its owner. The availabledata were a daily count of Obama nungara’s abundance since June 2020 combined with nationalmeteorological data. It provides us with a full dataset to describe fine-scale population dynamics usingBayesian linear models and to assess whether climate or weather has consequences on the abundance ofObama nungara.