Effects of demographic stochasticity on biological community assembly on evolutionary time scales

TL;DR

This study investigates how demographic stochasticity influences long-term biological community assembly and evolution, revealing that noise significantly affects diversity, stability, and fluctuation patterns in predator-prey models.

Contribution

It demonstrates the impact of demographic stochasticity on community diversity, stability, and fluctuation dynamics, highlighting differences between mutualistic and predator-prey communities.

Findings

Demographic stochasticity has little effect on mutualistic communities.

Predator-prey models show decreased diversity and population size with noise.

Noise induces 1/f fluctuations in community dynamics.

Abstract

We study the effects of demographic stochasticity on the long-term dynamics of biological coevolution models of community assembly. The noise is induced in order to check the validity of deterministic population dynamics. While mutualistic communities show little dependence on the stochastic population fluctuations, predator-prey models show strong dependence on the stochasticity, indicating the relevance of the finiteness of the populations. For a predator-prey model, the noise causes drastic decreases in diversity and total population size. The communities that emerge under influence of the noise consist of species strongly coupled with each other and have stronger linear stability around the fixed-point populations than the corresponding noiseless model. The dynamics on evolutionary time scales for the predator-prey model are also altered by the noise. Approximate $1/f$ fluctuations are observed with noise, while $1/f^{2}$ fluctuations are found for the model without demographic noise.