Ants are famous for their regimented and complex social behaviors. In the tropics, they are also famous for forming mutualisms with plants. Certain species of trees have conspicuous hollow swellings that house ants, often feeding the ants with specialized ant food. In return, the ants are pugnacious bodyguards, swarming out to aggressively defend the plant against enemies. Scientists have observed these mutualisms for centuries, but an enduring question is how these intriguing interactions evolved in the first place.
That remains a mystery, but new research led by University of Utah field biologist Rodolfo Probst offers insights that could broaden our understanding of ant-plant symbioses.
Published last week in the Proceedings of the Royal Society B, his research focused on an ant genus called Myrmelachista. Most Myrmelachista species nest in dead or live stems of plants, without any specialized mutualistic association. But one group of species in Central America was known to nest only in the live stems of certain species of small understory trees, in a specialized symbiosis similar to other ant-plant mutualisms. These tiny yellow ants hollow out the stems without harming the host plants, and can be found throughout Central America.
Jack Longino. Credit: Rodolfo Probst
Probst made a remarkable discovery. Using DNA sequence data to unravel their evolutionary history, he found that these nine species occurred as two clusters in different parts of the evolutionary tree. That means that this complex relationship, with all its distinctive characteristics, evolved twice from non-specialist ancestors.
His two coauthors are renowned entomologist Jack Longino, better known among U students as The Astonishing Ant Man for his expertise and vast personal collection of ant specimens kept on campus, and former U School of Biological Sciences’ postdoctoral researcher Michael Branstetter, now with U.S. Department of Agriculture’s Pollinating Insect Research Unit at Utah State University.
Probst is a postdoctoral researcher in the School of Biological Sciences and the university’s Science Research Initiative, or SRI, and was recently recognized with the Outstanding Postdoctoral Researcher Award by the College of Science. Through the SRI, Probst has involved U undergraduates in his research. For example, students accompanied Probst and Longino to Costa Rica with funding support from the U’s Wilkes Center for Climate Science & Policy.
With continuing help from SRI undergraduates, Probst is looking to conduct whole genomic sequencing to tease out the genes involved in ant-plant associations, looking “under the hood” of a phenomenon that has intrigued naturalists for centuries.
Read more about the story on ants and trees by Brian Maffly @TheU.