Figure 1. Interaction mechanisms in the multiplex model

Kayla Sale-Hale, a graduate student in ecology and evolutionary biology, is first author of a study published May 1, 2020 in Nature Communications titled “Pollinators in food webs: Mutualistic interactions increase diversity, stability and function in multiplex networks.”

“In this work, I've used ecological network models to synthesize different types of ecological interactions (predator-prey, plant-herbivore and plant-pollinator) and investigated the mechanisms of pollinator mutualism that affect ecosystem stability and function,” explained Sale-Hale. “This is a critical topic because of a prominent historical result that mutualisms like animal pollination should destabilize complex ecological networks due to positive feedbacks but are nonetheless ubiquitous in real ecosystems.”

Pollinators provide a critical ecosystem service, but it is less well-known that they feed and are fed upon by a highly interconnected network of plants, animals and parasites and that this complexity has controversial effects on ecosystem dynamics. Here, the authors show that when mutualists such as pollinators are included in food webs, they increase biodiversity, stability and function in complex ecosystems. 

The paper describes a solution to a well-known contradiction between data and theory about ecosystems. Classic theory holds that when species help each other, as with pollinators and plants and many other mutualisms, ecosystems are destabilized because mutual dependencies amplify booms and busts thus causing extinctions. But data tells us that mutualisms are pervasive in ecosystems, especially among plants and their fungal symbionts, animal seed dispersers and human farmers.  

“My paper resolves this contradiction by developing more realistic computer models that illustrate for the first time how mutualism leads to more stable, diverse and productive ecosystems in complex networks of many interacting species. The lack of computational power prevented earlier scientists from more accurately modeling complex ecological networks and understanding how such positive effects could emerge.”

Coauthors are EEB Professor Fernanda Valdovinos, who is Sale-Hale’s advisor, and Nio Martinez, University of Arizona.

Sale-Hale won a Volterra award at the 2018 Ecological Society of America meeting for a presentation on this work. Read more in previous web news.

Compiled by Gail Kuhnlein