Environmental weakening of trophic interactions drives stability in stochastic food webs

The physiological performance and behaviour of organisms are contingent on environmental conditions. When these conditions vary over time, this can have important consequences for the dynamics of individual populations and entire species communities. While the importance of environmental variation on the structuring and stability of natural food webs is recognised, little work has been done so far to build up a theoretical understanding of these processes. Here we investigate a simple model food web, where a consumer species forages flexibly upon two distinct, inter-competing resource species. Resource productivities or the resource intake rates by the consumer are assumed to depend on environmental conditions in a realistic manner. Fluctuations in these parameters drive variation in the strength of consumer-resource interactions, depending on whether the resource or the consumer is sensitive to environmental noise. The way resources and the consumer respond to changes in environmental conditions stems from the deterministic influence of each stochastic parameter on food web dynamics, which interact with the consumer adaptation process as well as between-resource competition. According to recent empirical reports, the mechanisms behind our results are likely to be relevant in natural systems and thus the model predictions are of potential importance in understanding food web responses to environmental stochasticity in general.