Stochastic fluctuations in an eco-evolutionary game dynamics with environmental feedbacks

TL;DR

This paper analyzes how stochastic fluctuations affect eco-evolutionary game dynamics with environmental feedbacks, showing that population sizes fluctuate around equilibrium with variance linked to environmental capacity, validated by simulations.

Contribution

It extends deterministic eco-evolutionary models to include stochastic effects using the $ ext{Ω}$-expansion, revealing stability properties under environmental feedbacks.

Findings

Population size fluctuations are around the deterministic equilibrium.

Variance of fluctuations is proportional to environmental carrying capacity.

Simulation results confirm the validity of the $ ext{Ω}$-expansion approximation.

Abstract

Building upon the eco-evolutionary game dynamics framework established by Tilman et al., we investigate stochastic fluctuations in a two-strategy system incorporating environmental feedback mechanisms, where the payoff matrix exhibits population size dependence. We adopt a systematic approach which is the so-called $\Omega$-expansion. When the stochastic factor is integrated, it is shown that the population size for each strategy fluctuates around the interior equilibrium of the macroscopic equations (corresponding to the deterministic model of the eco-evolutionary game) and its variance converges to a constant that is proportional to the environmental carrying capacity if the interior equilibrium is asymptotically stable. The simulation results demonstrate that the $\Omega$ expansion provides a valid approximation, and the reliability of the aforementioned conclusions is verified. Therefore, analogous to Fudenberg and Harris' s stochastic replicator dynamics for infinite populations under external noise (\emph{J. Econ. Theory 57, 420-441}), the dynamic stability of the eco-evolutionary game can be extended to the stochastic regime when the environmental carrying capacity is sufficiently large.