Abstract

Theoretical predictions regarding trophic cascades, the positive indirect effect of a predator on a resource, are challenged by empirical observations reporting variations in their signs and magnitude. A limitation is that theory focuses on simple food chains while those are embedded into complex food webs in nature. Using simulated and empirical food webs, we generalize the concept of trophic cascade to whole food webs where longer-order indirect effects trickling across multiple species can influence trophic cascade patterns. We find that indirect effects generate divergences from the classic trophic cascade scheme, leading to a diversity of cascade behavior. Divergences occur both in trophic chains embedded within food webs, but also when species are aggregated into trophic levels. From this perspective, the classic cascade is a specific case occurring only when longer-order indirect effects are negligible. Indirect pathways could be prevalent on the dynamic of species in food web exhibiting collective behavior.