The ecological biogeography of indigenous and introduced Antarctic springtails.
Aim: We investigated turnover and richness in Antarctic springtails to understand large-scale patterns in soil faunal diversity and how these are altered by biological invasions. Location: Antarctica and the Southern Ocean Islands. Taxon: Collembola (springtails). Methods: We developed a database of all springtail species recorded from the Antarctic region. The relationship of species richness and turnover to high-resolution environmental data was explored using generalized linear models and generalized dissimilarity models, and compared among indigenous and introduced species. Endemicity and species turnover were assessed using beta-diversity and multi-site zeta diversity metrics to explore whether introduced species have homogenized assemblages across the region. Results: Indigenous, endemic and introduced species richness covaried positively with temperature. Endemic richness was further related to thermal heterogeneity, and introduced species richness to human occupancy. Indigenous and introduced species richness covaried positively. Species turnover across the region was high, and the introduction of non-indigenous species further differentiated assemblages. Species similarity between sites was not related to distance, nor was geographic isolation correlated with species richness. Assemblage turnover was influenced by the area and temperature range of islands. Main conclusions: Energy availability appears to be the primary covariate of species richness, with human presence additionally influencing introduced species richness, in agreement with other soil-dwelling taxa. Dispersal limitation surprisingly does not seem to be important in structuring these assemblages, nor does island age appear to affect richness; this may in part reflect the severe glacial history of the region. The differentiating effect of introduced species on assemblages suggests that anthropogenic introductions originate from distinct source pools, challenging common assumptions for the Antarctic. Positive covariance between indigenous and introduced species richness accords with the "rich get richer" hypothesis. Thus, the most biotically diverse terrestrial areas of Antarctica may be the most prone to future biological invasion.