Dominance to egalitarian transition in diverse communities

TL;DR

This paper investigates how stochastic dynamics and niche overlap influence community structure, revealing a transition from dominance by few species to an egalitarian distribution among many, supported by empirical data.

Contribution

It introduces a theoretical framework explaining the dominance-egalitarian transition in diverse communities, emphasizing the role of demographic stochasticity.

Findings

Identification of two community phases: dominance and egalitarian

Validation of theory with empirical data from hyperdiverse communities

Demonstration of stochasticity's role in shaping species abundance patterns

Abstract

Diverse communities of competing species are generally characterized by substantial niche overlap and strongly stochastic dynamics. Abundance fluctuations are proportional to population size, so the dynamics of rare populations is slower. Hence, once a population becomes rare, its abundance gets stuck at low values. Here, we analyze the effect of this phenomenon on community structure. We identify two different phases: a dominance phase, in which a tiny number of species constitute most of the community, and an egalitarian phase, where it takes a finite fraction of all species to constitute most of the community. We demonstrate the validity of the theory using empirical findings for a variety of hyperdiverse communities, and clarify the role of demographic stochasticity in shaping patterns of commonness and rarity.