The environmental dependence of ecological interaction networks

Interactions between species are often assumed to occur whenever species pairs co-occur, allowing us to reconstruct local ecological networks from a deterministic 'metaweb'. Over the past few years, an increasing number of papers have called for a reassessment of this simplistic assumption. This new literature addresses how stochasticity in the occurrence of species and links, and environmental imprints on these, shape ecological interaction networks. In this review, we systematically demonstrate the imprints of stochasticity and environmental dependence on ecological interaction networks using both simulations and empirically-characterised networks. We find that both species and link occurrence are stochastic, with probabilities conditional on the environment. This insight improves our ability to model observed variation in network structures. We argue that future research should incorporate environmental impacts on both species and links, effectively abandoning the deterministic view on interactions and moving away from the metaweb approach.