Correlation between interaction strengths drives stability in large ecological networks

TLDR

Food webs exhibit markedly non‑random structure, which ecologists argue is essential for stability because large random ecological networks would be unstable and thus not observed empirically. The study demonstrates that the correlation between consumer effects on resources and resource effects on consumers largely explains food‑web stability. Random food webs that preserve the distribution and correlation of interaction strengths exhibit stability comparable to empirical systems, revealing that topological structure has a minor influence and that stability analyses must first consider interaction‑strength distribution and correlation.

Abstract

Abstract Food webs have markedly non‐random network structure. Ecologists maintain that this non‐random structure is key for stability, since large random ecological networks would invariably be unstable and thus should not be observed empirically. Here we show that a simple yet overlooked feature of natural food webs, the correlation between the effects of consumers on resources and those of resources on consumers, substantially accounts for their stability. Remarkably, random food webs built by preserving just the distribution and correlation of interaction strengths have stability properties similar to those of the corresponding empirical systems. Surprisingly, we find that the effect of topological network structure on stability, which has been the focus of countless studies, is small compared to that of correlation. Hence, any study of the effects of network structure on stability must first take into account the distribution and correlation of interaction strengths.