Getting antsy in the preserves

University of St. Francis researchers study how ants disperse seeds

|  Story by Cindy Cain |


The Forest Preserve District has ants in its plants, which is the perfect scenario for a University of St. Francis research team.

The team is looking at the relationship between ants and plants and the role the insects play in dispersing seeds.

The subject matter may be small, but the results are intriguing and helpful for the environment, said Chloe Lash, an assistant professor of biology at the school who is leading the team.

“I think that studying ants offers a unique perspective on the world,” she said. “These tiny little animals, that we walk over every day or that we complain about when they are in our kitchens, are so vital to our natural spaces.

“Ants plant the forest understory – next time you go for a spring wildflower walk, be sure to thank the ants,” she added. “They also provide other important services to the ecosystem, like turning soil and helping with decomposition. The littlest organisms are often the most important for the function of our planet!”

The ants Lash and her team are studying in Will County preserves are called aphaenogaster, or winnow ants.

Hotspot for ant, plant connection

Chloe Lash holding a seed with ants on it.

Ants disperse seeds all over the world, and our area is a “hotspot” for this relationship, Lash said.

The technical name for this dispersal is myrmecochory, which is of mutual benefit to both the ants and the plants.

“The plant gets a reward, and the ant gets a reward,” she said.

Here’s how the relationship between ants and plants works, according to Lash:

Seeds of certain plants have a fleshy part that is known as the elaiosome. The ants are attracted to the elaiosome because it is a food source.

“They pick up the seeds (after they fall from the parent plant) and return the seeds to their ant nest,” she said. “They remove the elaiosome and eat it (or feed it to the baby ants) and then spit the rest of the seed outside of the nest, which is where the seed can grow into a new plant.”

The ants get food, and the seeds wind up in a new and beneficial location, she said.

“Many of the herbaceous understory plants of the forest (up to 35%) are ant dispersed,” she added.

Chemical connection

A collection of ants Chloe Lash is studying.

Lash and her team are studying the bacteria, fungi and chemicals that are a part of this interaction.

“Plants and ants produce a lot of chemicals and some of those chemicals are used by the plants and ants for defense against their pathogens,” she said. “I'm interested in seeing how those chemicals affect the partners in this mutualism. So, I investigate how ants and their chemicals impact plants and their pathogens and how plants and their chemicals impact ants and their pathogens.”

The study is regional, but the plants and ants that USF researchers are studying are widespread around the eastern United States.

“Much of my work is done in the lab,” she added. “So, we collect ants and seeds and bring them back to University of St. Francis campus, where we can run some experiments with individual ants, ant colonies, and the seeds.”

The USF team is investigating ant preference for different seed types.

“This will help us understand choices that the ants make in natural settings, and this could be important for ant survival and plant dynamics,” Lash said.

Invasive needle ant

A flag in the ground.

Microbes also play a role. Microbes are microorganisms, especially bacterium that cause disease or chemical breakdown.

“To understand how ants are changing the microbes on seeds, we need to know what chemicals the ants produce,” she explained.

Lash is working with Dr. Scott Gruenbaum, an assistant professor of chemistry at the university, to study chemicals that are in ant glands and what properties they have.

“We have found some chemicals with antimicrobial properties, which means these chemicals inhibit the growth of fungi and bacteria,” she said.

Lash said the goal of the work is to understand the ant-plant interaction more fully and how it came about and why it continues to persist. She noted that other parts of the country, mostly the southeast, are dealing with native ants being displaced by the invasive Asian needle ant.

“We hope that by more fully understanding the mutualism between ants and plants, we cannot only help mitigate the invasion, but we can also predict the impact that the invasion will have on native plants,” Lash said. “The invasive species is not near Illinois yet, and we are hoping that it stays that way!”

Photos by Anthony Schalk

Chloe Lash sitting at a picnic table.
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