Dissecting global turnover in vascular plants

AimTo provide a global assessment of turnover in vascular plants across geographical settings and taxonomic and functional groups. We tested whether turnover and its spatial and environmental drivers are affected by the geographical setting and whether taxonomic and functional groups exhibit specific turnover patterns that are associated with their ecological characteristics. LocationGlobal. MethodsWe collated a global dataset of vascular plant checklists comprising 258 island and 346 mainland units. We created subsets based on the geographical setting of study units (mainland, islands, different island types) as well as taxonomic and functional properties of species (angiosperms, gymnosperms, pteridophytes, trees, shrubs, herbs). For the entire dataset, and each subset, the distance decay of similarity was assessed using generalized linear models. To disentangle the relative importance of spatial and environmental drivers of turnover, we employed generalized dissimilarity models. Finally, the model results were used to predict compositional similarity of vascular plants across a global grid. ResultsThe distance decay of similarity was stronger for mainland units than for islands. Among taxonomic and functional groups, the rate of decay was lowest for pteridophytes and highest for shrubs. Partitioning of turnover into distance- and environment-related effects revealed fundamental differences between mainland and island systems, with geographical distance being more important on the mainland than on islands. This trend was consistent across taxonomic and functional groups. Main conclusionsOur results reveal an important role of geographical context in shaping beta-diversity patterns. We argue that geographical settings are characterized by specific configurations of ecological filters that have a strong impact on the magnitude and structure of turnover. Moreover, taxonomic and functional groups are differentially successful in passing these filters, resulting in group- and setting-specific turnover patterns. Exploring these interdependences for different taxa and geographical settings at different scales will help to improve our understanding of beta diversity.