Terrestrial macro-arthropods of the sub-Antarctic islands of Possession (Crozet Archipelago) and Kerguelen: inventory of native and non-native species

The sub-Antarctic islands of the Southern Ocean harbor biogeographically peculiar biotas which are under threat from climate change, biological invasions and their interactions. Understanding both the indigenous and changing non-indigenous components of these islands is essential for the conservation and management of their biotas. Based on several years of systematic sampling, we present an updated list of terrestrial, free-living macro-invertebrates (insects and spiders) present on the islands of Possession (Crozet Archipelago) and Kerguelen. Ninety-four species were recorded in total on both islands. Forty-one are strictly endemic to one of the two islands, 16 are endemic to the South Indian Ocean Province, and only three were recorded on other sub-Antarctic islands. Beetles and more particularly weevils are the most characteristic group of the fauna of these islands: they include 35 species of which 89% are native and 66% are endemic. One third of the species (30 of 94) are non-indigenous species now naturalized. We discuss these results in terms of biogeography, ecological disharmony and impact of biological invasions.