Biotic filtering by species’ interactions constrains food-web variability across spatial and abiotic gradients

Despite intensive research on species dissimilarity patterns across
communities (i.e. beta-diversity), we still know little about their
implications for variation in food-web structures. Our analyses of 50 lake
and 48 forest soil communities show that, while species dissimilarity
depends on environmental and spatial gradients, these effects are only
weakly propagated to the networks. Moreover, our results show that species
and food-web dissimilarities are consistently correlated, but that much of
the variation in food-web structure across spatial, environmental, and
species gradients remains unexplained. Novel food-web assembly models
demonstrate the importance of biotic filtering during community assembly
by (1) the availability of resources, and (2) limiting similarity in
species’ interactions to avoid strong niche overlap and thus competitive
exclusion. This reveals a strong signature of biotic filtering processes
during local community assembly, which constrains the variability in
structural food-web patterns across local communities despite substantial
turnover in species composition.