Neutral theory of cooperative dynamics

TL;DR

This paper introduces a stochastic neutral theory for cooperative species, explaining how cooperation influences biodiversity and species abundance distributions in ecosystems, with analytical results applicable across different migration regimes.

Contribution

It develops a neutral model incorporating cooperation among species, extending classic neutral theory to account for mutualistic interactions and their effects on biodiversity.

Findings

Bimodal species-abundance distribution with a core of cooperative species

Analytical expressions for steady-state species abundance distribution

Scaling laws for diversity, species number, and residence times

Abstract

Mutualistic interactions are widespread in nature, from plant communities and microbiomes to human organizations. Along with competition for resources, cooperative interactions shape biodiversity and contribute to the robustness of complex ecosystems. We present a stochastic neutral theory of cooperator species. Our model shares with the classic neutral theory of biodiversity the assumption that all species are equivalent, but crucially differs in requiring cooperation between species for replication. With low migration, our model displays a bimodal species-abundance distribution, with a high-abundance mode associated with a core of cooperating species. This core is responsible for maintaining a diverse pool of long-lived species, which are present even at very small migration rates. We derive analytical expressions of the steady-state species abundance distribution, as well as scaling laws for diversity, number of species, and residence times. With high migration, our model recovers the results of classic neutral theory. We briefly discuss implications of our analysis for research on the microbiome, synthetic biology, and the origin of life.