Penn professor's research shows ecosystems with mutualism can be stable

New research from a Penn professor and a Penn alum shows that mutually beneficial relationships between species can exist in stable ecosystems, contradicting previous research.

Erol Akçay, assistant professor of biology, and 2019 College graduate Jimmy Qian wrote that ecosystems with mutualism can also resist invasion in a paper published in Nature Ecology and Evolution this week. Their research contradicts classical ecological models, which argue that mutual interactions create instability, Penn Today reported.

Mutualistic interactions are ecological relationships where two organisms both benefit, such as when bees pollinate flowers.

Previous ecological models argued that complex ecosystems tend to be more unstable because an increase in one species leads to an increase in another, Akçay told Penn Today. Akçay and Qian showed that the balance of ecological forces, such as competition, also has an impact on stability, Penn Today reported.

Akçay and Qian built models that relied on different assumptions than past research, Penn Today reported. They assumed that benefits from mutualistic relationships will exhaust at a certain limit, and that species arrive in ecosystems in a particular order rather than all at once. By building sequential models, Akçay and Qian measured external stability, which quantifies an ecosystem's ability to resist invasion by a new species. They found that mutualism increases external stability, Penn Today reported.

“The reason is blindingly obvious in retrospect. If you have a community where most of the species are helping each other, each species will be abundant. If you are at this tiny population size and are trying to invade this community, it will be hard because your competitors are thriving,” Akçay told Penn Today.