A niche for neutrality

TLDR

Ecologists recognize that species‑abundance patterns alone cannot resolve the debate between niche and neutral processes, with the neutral model representing a special case of absent stabilizing mechanisms and equivalent fitness. The study reframes the niche–neutral debate using classical coexistence theory, aiming to assess how much observed diversity is driven by strong stabilizing mechanisms that overcome fitness differences versus weak stabilization among similarly fit species. They propose integrating per‑capita growth‑rate data with models to quantify stabilizing processes, measure fitness inequality, compare the two, and manipulate frequency dependence to test how stabilization and fitness equivalence affect coexistence.

Abstract

Ecologists now recognize that controversy over the relative importance of niches and neutrality cannot be resolved by analyzing species abundance patterns. Here, we use classical coexistence theory to reframe the debate in terms of stabilizing mechanisms (niches) and fitness equivalence (neutrality). The neutral model is a special case where stabilizing mechanisms are absent and species have equivalent fitness. Instead of asking whether niches or neutral processes structure communities, we advocate determining the degree to which observed diversity reflects strong stabilizing mechanisms overcoming large fitness differences or weak stabilization operating on species of similar fitness. To answer this question, we propose combining data on per capita growth rates with models to: (i) quantify the strength of stabilizing processes; (ii) quantify fitness inequality and compare it with stabilization; and (iii) manipulate frequency dependence in growth to test the consequences of stabilization and fitness equivalence for coexistence.