The invasion of Obama nungara (Platyhelminthes: Geoplanidae) in metropolitan France and its impact on earthworm communities.
Résumé
Obama nungara (Platyhelminthes: Geoplanidae) is a terrestrial flatworm native to South America and considered invasive in France, with a reported presence in three quarters of France. To date, it has only been recorded in anthropized habitats such as private gardens. This species is a known predator of earthworms which play an essential role in soil ecosystems, for instance through decomposition of organic matter and by digging galleries ensuring soil aeration. In temperate areas, earthworm species may be roughly classified in three ecotypes (i.e. epigeic, anecic and endogeic) that may have various impacts on soil 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 soil ecosystems. The present study is part of a project that aims to understand the impact of O. nungara on earthworm communities and on soil functioning. Here, our main objective was to describe the dynamics of O. nungara populations in introduced sites of metropolitan France, in relation to the structure of earthworm communities. Thus, we monitored twice a year (Autumn and Spring) the abundance of O. nungara, the abundance of earthworms and their community structure, in 10 different sites (private gardens, greenhouse and 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 available data were a daily count of Obama nungara’s abundance since June 2020 combined with national meteorological data. It provides us with a full dataset to describe fine-scale population dynamics using Bayesian linear models and to assess whether climate or weather has consequences on the abundance of Obama nungara.