Growth tradeoffs produce complex microbial communities on a single limiting resource

TL;DR

This study demonstrates that variations in microbial growth traits on a single resource can generate complex community dynamics, including multistability and non-transitive interactions, without the need for additional ecological interactions.

Contribution

It reveals that higher-order ecological effects can emerge solely from trait variation in microbial growth on a single resource, expanding understanding of community complexity.

Findings

Multiple strains can coexist with multistability and neutral coexistence.

Pairwise coexistence does not guarantee coexistence in larger communities.

The best competitor in pairwise tests may not dominate in mixed communities.

Abstract

The relationship between the dynamics of a community and its constituent pairwise interactions is a fundamental problem in ecology. Higher-order ecological effects beyond pairwise interactions may be key to complex ecosystems, but mechanisms to produce these effects remain poorly understood. Here we show that higher-order effects can arise from variation in multiple microbial growth traits, such as lag times and growth rates, on a single limiting resource with no other interactions. These effects produce a range of ecological phenomena: an unlimited number of strains can exhibit multistability and neutral coexistence, potentially with a single keystone strain; strains that coexist in pairs do not coexist all together; and the champion of all pairwise competitions may not dominate in a mixed community. Since variation in multiple growth traits is ubiquitous in microbial populations due to pleiotropy and non-genetic variation, our results indicate these higher-order effects may also be widespread, especially in laboratory ecology and evolution experiments.