Community-level cohesion without cooperation

TL;DR

This paper introduces a minimal theoretical model showing that community survival during coalescence depends on community-level fitness rather than individual species performance, highlighting cohesion without cooperation.

Contribution

It formalizes a community-level perspective where cohesion arises from division of labor without requiring cooperation, extending MacArthur's model to community interactions.

Findings

Community survival is predicted by community-level fitness.

Cohesion can emerge without cooperation.

Model applies to microbial ecosystems.

Abstract

Recent work draws attention to community-community encounters ("coalescence") as likely an important factor shaping natural ecosystems. This work builds on MacArthur's classic model of competitive coexistence to investigate such community-level competition in a minimal theoretical setting. It is shown that the ability of a species to survive a coalescence event is best predicted by a community-level "fitness" of its native community rather than the intrinsic performance of the species itself. The model presented here allows formalizing a macroscopic perspective whereby a community harboring organisms at varying abundances becomes equivalent to a single organism expressing genes at different levels. While most natural communities do not satisfy the strict criteria of multicellularity developed by multi-level selection theory, the effective cohesion described here is a generic consequence of division of labor, requires no cooperative interactions, and can be expected to be widespread in microbial ecosystems.