Geodiversity of a European river network controls algal biodiversity and function

Abstract Biodiversity and functioning often follow spatial gradients, yet with unclear causal linkage. In spatially complex rivers, regional-scale factors associated with hydrological connections and catchment properties control downstream transport of material and dispersal of organisms, both being crucial for ecosystem functioning. In a single snapshot study, we here show how a river’s network structure interacts with its terrestrial matrix to control key environmental conditions and periphyton community composition at the local habitat scale, which in turn drive primary production. We found the high geodiversity of the Vjosa River network to promote high periphyton beta-biodiversity through regional (dispersal) and local (species sorting) processes. Community turnover driven by species sorting rather than purely by dispersal was identified as relevant for production rates, suggesting a match between environment and community composition to be conditional for functioning. Hence, anthropogenic perturbation of regional mechanisms by river modification may affect ecosystem functions through interfering with metacommunity structure.