Seasonal Metacommunity Processes of Benthic Invertebrates in the Vjosa/Aoos River

ABSTRACT There are only a handful of free‐flowing rivers left on our planet. The unique biodiversity in these model systems offers a key to understanding the structures of naturally assembled fluvial metacommunities. Here, we use the benthic invertebrate fauna of the Vjosa River as a model system to infer metacommunity processes from biodiversity patterns at river network scale. To this end, we used data from standard, morphology‐based and metabarcoding approaches to describe community composition at 36 sites in spring and autumn. Classical ordination as well as joint species distribution modeling indicate that community composition in headwaters is mostly defined by (likely limited) dispersal and environmental filtering, whereas communities at downstream sites in the main stem are shaped more by associations among taxa. At the population level of individual taxa, the relative importance of spatial factors, environmental filtering, and potential associations to other taxa changed between seasons. Our study provides a realistic impression of the ecology of fluvial metacommunities under the fluctuating influences of spatial structure, environmental conditions, and biotic interactions in a free‐flowing river network.