Stability of two-species communities: drift, environmental stochasticity, storage effect and selection

TL;DR

This paper develops a comprehensive theory for the persistence time of two-species communities, incorporating drift, environmental stochasticity, and selection, to better understand species coexistence and extinction times.

Contribution

It introduces a general framework that combines demographic stochasticity, environmental variability, and selection to analyze community persistence times.

Findings

Persistence time depends on the interplay of drift, environmental stochasticity, and selection.

Environmental stochasticity can significantly extend community coexistence.

The model unifies previous results for neutral and strongly selected systems.

Abstract

The dynamics of two competing species in a finite size community is one of the most studied problems in population genetics and community ecology. Stochastic fluctuations lead, inevitably, to the extinction of one of the species, but the relevant timescale depends on the underlying dynamics. The persistence time of the community has been calculated for neutral models, where the only drive of the system is drift (demographic stochasticity) and for models with strong selection. Following recent analyses that stress the importance of environmental stochasticity in empirical systems, we present here a general theory of persistence time of two-species community where drift, environmental variations and time independent selective advantage are all taken into account.