The effect of environmental stochasticity on species richness in neutral communities

TL;DR

This paper explores how environmental stochasticity influences species richness in neutral communities, revealing a complex interplay where increased environmental variability can either destabilize or stabilize biodiversity depending on the correlation time of environmental changes.

Contribution

It introduces a metacommunity neutral model incorporating environmental stochasticity and demographic noise, analyzing how these factors affect species richness and stability.

Findings

Species richness dependence on environmental stochasticity changes sign with correlation time.

Demographic noise is crucial for realistic model behavior.

Storage effect's stabilizing role diminishes with longer environmental correlation times.

Abstract

Environmental stochasticity is known to be a destabilizing factor, increasing abundance fluctuations and extinction rates of populations. However, the stability of a community may benefit from the differential response of species to environmental variations due to the storage effect. This paper provides a systematic and comprehensive discussion of these two contradicting tendencies, using the metacommunity version of the recently proposed time-average neutral model of biodiversity which incorporates environmental stochasticity and demographic noise and allows for extinction and speciation. We show that the incorporation of demographic noise into the model is essential to its applicability, yielding realistic behavior of the system when fitness variations are relatively weak. The dependence of species richness on the strength of environmental stochasticity changes sign when the correlation time of the environmental variations increases. This transition marks the point at which the storage effect no longer succeeds in stabilizing the community.