Neutral dynamics with environmental noise: age-size statistics and species lifetimes

TL;DR

This paper extends neutral ecological and genetic models by incorporating environmental noise, showing that it significantly alters species lifetime predictions and aligns better with empirical data.

Contribution

It introduces a framework combining demographic and environmental stochasticity, improving the realism of neutral models in explaining species dynamics.

Findings

Environmental noise controls long-term species dynamics.

Modified models better match empirical species lifetime data.

Different types of environmental noise have distinct impacts on community stability.

Abstract

Neutral dynamics, where taxa are assumed to be demographically equivalent and their abundance is governed solely by the stochasticity of the underlying birth-death process, has proved itself as an important minimal model that accounts for many empirical datasets in genetics and ecology. However, the restriction of the model to demographic [${\cal{O}} ({\sqrt N})$] noise yields relatively slow dynamics that appears to be in conflict with both short-term and long-term characteristics of the observed systems. Here we analyze two of these problems - age size relationships and species extinction time - in the framework of a neutral theory with both demographic and environmental stochasticity. It turns out that environmentally induced variations of the demographic rates control the long-term dynamics and modify dramatically the predictions of the neutral theory with demographic noise only, yielding much better agreement with empirical data. We consider two prototypes of "zero mean" environmental noise, one which is balanced with regard to the arithmetic abundance, another balanced in the logarithmic (fitness) space, study their species lifetime statistics and discuss their relevance to realistic models of community dynamics.