Once upon a time in the south: local drivers of plant invasion in the harsh sub-Antarctic islands

Aim: To investigate the local effect of environmental and human-related factors on alien plant invasion in sub-Antarctic islands. To explore the relationship between alien species features and dependence on anthropogenic propagule pressure to unravel key traits conferring invasiveness in the sub-Antarctic.Location: Possession Island, Crozet archipelago (French sub-Antarctic islands).Taxon: Non-native vascular plants (Poaceae, Caryophyllaceae, Juncaceae).Methods: Single-species distribution models were used to explore the effect of high-resolution topoclimatic and human-related variables on the occurrence of six of the most aggressive alien plants colonizing French sub-Antarctic islands. Furthermore, the interaction between alien species traits and their response to anthropogenic propagule pressure was analysed by means of a multi-species distribution model. This allowed identifying the features of species that were associated to low dependence on human-assisted introductions, and were thus potentially more invasive.Results: We observed two main invasion patterns: low-spread species strongly dependent on anthropogenic propagule pressure and high-spread species limited mainly by harsh climatic conditions. Differences in invasiveness across species mostly related to their residence time, life history and plant height, with older introductions, perennial and low-stature species being most invasive.Main conclusions: The availability of high-resolution data allowed for a fine understanding of the role of environmental and human-related factors in driving alien species distribution on sub-Antarctic islands. At the same time, the identification of alien species features conferring invasiveness may help anticipating future problematic invasions