Distribution and cover of a recently introduced alien sedge species, Carex pilulifera L., in the subalpine vegetation of Reunion Island

Carex pilulifera L., a perennial herb native to Europe, was recently introduced and found in subalpine vegetation of Reunion Island. In this study, we assessed the current distribution and cover of C. pilulifera within the subalpine vegetation (Piton des Neiges and Piton de la Fournaise) of the National Park of Reunion. We used GLM models to analyse relationships between C. pilulifera and habitat, disturbance type, and proximity to fodder and grazing areas. We evaluated the potential distribution of C. pilulifera using species distribution models. Presence of C. pilulifera was only found on Piton de la Fournaise with a mean cover of 16.6% (where present). Carex pilulifera was the fourth most observed alien species (27% of all observations). According to the SDM, it could also occur in Piton des Neiges but was not found. Carex pilulifera was significatively more present in subalpine grasslands and close to grazing and fodder areas. . We believed fodder and grazing areas to be the introduction pathways of this species. This study confirmed the status of C. pilulifera as an invasive species in the subalpine vegetation of Reunion Island which comprises a high level of plant endemism. We suggest that management should primarily focus on surveying potentially suitable areas in Piton des Neiges to eradicate new introduction and to control the species within high biodiversity areas in Piton de la Fournaise.