An 8-year-old boy’s observation in his backyard has contributed to a scientific finding that challenges over a century of assumptions about ant behavior.
Hugo Deans noticed a cluster of small rounded objects near an ant nest at his home. His father, Andrew Deans, a Penn State University entomology professor, identified them as oak galls, not seeds, and took note of how close they were to the nest.
That observation prompted a research collaboration between Penn State and SUNY. The team documented a three-way interaction among ants, oak trees, and gall-forming wasps that had not previously been recorded in scientific literature, according to their published findings.
Oak galls are small plant growths caused by insects. They act as enclosed chambers and serve as a microhabitat for developing larvae. The galls Hugo found were produced by gall wasps.
Ant Seed Dispersal Behavior Found to Extend Beyond Seeds
The study focused on galls from two cynipid wasp species, Kokkocynips rileyi and Kokkocynips decidua, which form on red oak leaves. The galls have a pale cap the researchers called the “kapéllo,” from the Greek word for “cap.” In late summer and autumn, when leaves fall, ants were observed collecting the capped galls and carrying them away.
Researchers ran field experiments in a New York forest, placing dishes containing bloodroot seeds alongside K. rileyi galls. Ants, particularly Aphaenogaster picea, a species already known for seed dispersal, removed the galls at roughly the same rate as the seeds over about 90 minutes.
In lab observations, ants grasped the galls by the kapéllo the same way they handle elaiosomes, the fatty attachments on certain seeds that ants eat for nutrients. When the kapéllo was removed from the galls, ants largely ignored them. With the cap intact, interest was strong.
Chemical analysis found the kapéllo contains free fatty acids also present in elaiosomes. Those compounds are known to trigger ants’ carrying behavior, explaining why the galls drew the same response as seeds.
“Ants get a little bit of nutrition when they eat the elaiosomes, and the plants get their seeds dispersed to an enemy-free space,” Andrew Deans said.
Forest Ecosystem Interactions More Complex Than Previously Understood
The researchers say the findings suggest that small chemical cues can influence how insects, nutrients, microbes, and predators move through ecosystems, and that overlooked species interactions may play a larger role in biodiversity than currently understood.
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