# Evolution of One Species Increases Resistance to Invasion in a Simple Synthetic Community

## TL;DR

A study shows that when two species coevolve over thousands of generations, they become better at resisting invasion by other species in a synthetic microbial community.

## Contribution

The study demonstrates that coevolution strengthens resistance to invasion by protecting a less dominant species in a synthetic community.

## Key findings

- E. coli protects S. cerevisiae from being outcompeted during invasion.
- Longer coevolution increases the protective effect of E. coli.
- A mathematical model explains how coevolution leads to community protection.

## Abstract

The species that make up a microbial community determine its potential function. A major goal of microbial ecology is to make assemblages of microbes — synthetic communities — with targeted applications. Replacing a dysfunctional community with a synthetic microbial community can have transformative impacts upon a host or ecosystem, yet the introduced community may be outcompeted by local species or communities, resulting in transient effects. Here, we study a simple synthetic community comprised of two species — E. coli and S. cerevisiae — that have coevolved for either 0, 1000 or 4000 generations, and evaluate the potential for 12 bacterial strains, from five species, to invade. We find that the dominant species (E. coli) in the community protects the less dominant species from being outcompeted during an invasion, and that this effect is strengthened by longer periods of coevolution. Using a mathematical model, we show how prolonged co-evolution leads to protective effects for a community member sensitive to displacement.

The online version contains supplementary material available at 10.1007/s00248-025-02618-w.