Demographic Fluctuations versus Spatial Variation in the Competition between Fast and Slow Dispersers

TL;DR

This paper investigates how demographic stochasticity influences the competition between fast and slow dispersers in spatially heterogeneous environments, revealing conditions where stochastic effects can reverse deterministic predictions.

Contribution

It introduces a simple model incorporating demographic stochasticity and resource competition, providing quantitative predictions of competitive outcomes based on environmental parameters.

Findings

Demographic stochasticity can reverse deterministic dispersal advantages.

The model predicts which disperser type wins under specific spatial and resource conditions.

Analytical results match simulations, validating the approach.

Abstract

Dispersal is an important strategy that allows organisms to locate and exploit favorable habitats. The question arises: given competition in a spatially heterogeneous landscape, what is the optimal rate of dispersal? Continuous population models predict that a species with a lower dispersal rate always drives a competing species to extinction in the presence of spatial variation of resources. However, the introduction of intrinsic demographic stochasticity can reverse this conclusion. We present a simple model in which competition between the exploitation of resources and stochastic fluctuations leads to victory by either the faster or slower of two species depending on the environmental parameters. A simplified limiting case of the model, analyzed by closing the moment and correlation hierarchy, quantitatively predicts which species will win in the complete model under given parameters of spatial variation and average carrying capacity.