Niche Overlap Is Not Enough: Same Overlap, Opposite Dynamics

Niche overlap (NO) is a central concept in coexistence theory, determining the outcome of competitive interactions at equilibrium. Yet, NO is a composite quantity that collapses multiple mechanisms and thus cannot by itself capture community dynamics. We quantify this gap by analyzing one of the simplest out-of-equilibrium observables: temporal correlations in species abundances, widely used in microbial ecology. Within a generalized consumer-resource framework, we separate the mechanistic traits that shape dynamical responses and show that systems with identical NO can display opposite correlation patterns. The decisive predictor is the yield–depletion mismatch (YDM) - the mismatch between species’ depletion and yield dissimilarities. Analytical theory, stochastic simulations, and a reanalysis of microbial time-series consistently show that YDM, not NO, sets the sign and magnitude of abundance correlations, whereas instantaneous growth-rate correlations increase with NO. Our results suggest that other out-of-equilibrium properties, such as invasion probabilities and coexistence robustness, will likewise be largely independent of NO and instead controlled by distinct out-of-niche parameters.