Tripartite networks show that keystone species can multitask

Abstract

AbstractThe importance of keystone species is often defined based on a single type of interaction (e.g., a keystone predator)1. However, all species participate in multiple types of interactions within their biological comunities2, and it remains unclear whether this functional importance extends across interaction types. Species interaction networks combining multiple types of interactions are quite well positioned to solve this puzzle, but so far results are contradictory3–7. We conducted a global meta-analysis of tripartite interaction networks to examine whether species functional importance in one niche dimension is mirrored in other niche dimensions. We show that the importance of keystone species is positively correlated across multiple dimensions of species’ ecological niche, independently from species’ abundance, interaction outcome (mutualistic/antagonistic) or intimacy (temporary/permanent interactions). These results show for the first time, that keystone species tend to be disproportionately relevant not only for one but for multiple ecosystem functions. Such multidimensionality of keystone species will likely have profound implications on the architecture, functioning, and resilience of entire ecosystems.