Niche Overlap Is Not Enough: Same Overlap, Contrasting Fluctuations

ABSTRACT

Niche overlap (NO) is a cornerstone of coexistence theory, summarising the strength of competitive coupling among species. Yet NO collapses distinct mechanisms into a single value and may miss key dynamical features. We quantify this limitation by examining temporal correlations in species abundances, a key out‐of‐equilibrium observable in microbial ecology. Using a MacArthur‐type consumer‐resource model, we show that communities with identical NO can display opposite dynamical patterns. Within the resource‐mediated fluctuation regime studied here, a yield‐depletion mismatch (YDM)—the difference between depletion and yield dissimilarities—consistently predicts the sign and magnitude of abundance correlations across analytical approximations, stochastic simulations, and a reanalysis of microbial time series. In contrast, growth‐rate correlations are governed by NO. More broadly, our results show that dynamical observables can depend on mechanistic details beyond those summarised by niche overlap.