Multiple peaks of species abundance distributions induced by sparse interactions

TL;DR

This paper explores how sparse, symmetric interactions in ecological communities influence species abundance distributions, revealing conditions for coexistence and the emergence of multiple peaks, supported by perturbative and non-perturbative theories and numerical simulations.

Contribution

It introduces a theoretical framework showing how sparse interactions cause multiple peaks in species abundance distributions, explaining observed ecological patterns.

Findings

All species coexistence in certain parameter ranges

Multiple peaks in abundance distributions due to discrete interactions

Robustness of coexistence and peaks confirmed by simulations

Abstract

We investigate the replicator dynamics with "sparse" symmetric interactions which represent specialist-specialist interactions in ecological communities. By considering a large self interaction $u$, we conduct a perturbative expansion which manifests that the nature of the interactions has a direct impact on the species abundance distribution. The central results are all species coexistence in a realistic range of the model parameters and that a certain discrete nature of the interactions induces multiple peaks in the species abundance distribution, providing the possibility of theoretically explaining multiple peaks observed in various field studies. To get more quantitative information, we also construct a non-perturbative theory which becomes exact on tree-like networks if all the species coexist, providing exact critical values of $u$ below which extinct species emerge. Numerical simulations in various different situations are conducted and they clarify the robustness of the presented mechanism of all species coexistence and multiple peaks in the species abundance distributions.