A generalized neutral theory explains static and dynamic properties of biotic communities

TL;DR

This paper extends neutral theory by incorporating environmental stochasticity, enabling it to accurately predict both static and dynamic properties of ecological communities, as demonstrated with tropical forest data.

Contribution

It introduces a generalized neutral theory that combines niche differences and stochasticity, improving predictions of community dynamics while maintaining simplicity.

Findings

Better fits to short-term fluctuation distributions

Improved modeling of temporal scaling of fluctuations

Accurate prediction of community compositional decay over time

Abstract

Understanding the forces shaping ecological communities is crucially important to basic science and conservation. In recent years, considerable progress was made in explaining communities using simple and general models, with neutral theory as a prominent example. However, while successful in explaining static patterns such as species abundance distributions, the neutral theory was criticized for making unrealistic predictions of fundamental dynamic patterns. Here we incorporate environmental stochasticity into the neutral framework, and show that the resulting generalized neutral theory is capable of predicting realistic patterns of both population and community dynamics. Applying the theory to real data (the tropical forest of Barro-Colorado Island), we find that it better fits the observed distribution of short-term fluctuations, the temporal scaling of such fluctuations, and the decay of compositional similarity with time, than the original theory, while retaining its power to explain static patterns of species abundance. Importantly, although the proposed theory is neutral (all species are functionally equivalent) and stochastic, it is a niche-based theory in the sense that species differ in their demographic responses to environmental variation. Our results show that this integration of niche forces and stochasticity within a minimalistic neutral framework is highly successful in explaining fundamental static and dynamic characteristics of ecological communities.