"The origin of fungus-farming ants was relatively well understood, but a more precise timeline for these microorganisms was lacking. The work provides the smallest margin of error to date for the emergence of these fungal strains, which were previously thought to be more recent," said Andre Rodrigues, a professor at the Institute of Biosciences of Sao Paulo State University (IB-UNESP) and co-author of the study.
Rodrigues leads a project funded by FAPESP and the U.S. National Science Foundation (NSF), focused on understanding the evolutionary relationship between ants and fungi. By analyzing the genomes of 475 species of fungi cultivated by ants, researchers were able to trace the evolutionary timeline back to the same period as the meteor impact.
Researchers identified two distinct fungal lineages that emerged almost simultaneously from a shared ancestor of the Attini, a group of ants that includes modern-day leafcutter ants. This discovery suggests that these ants may have begun cultivating fungi shortly after the mass extinction event, making them the earliest known farmers-well before humans began domesticating plants roughly 12,000 years ago.
The study also sheds light on the emergence of another fungus, known as coral fungi, which ants began cultivating about 21 million years ago. Coral fungi are named for their colony-like structures that resemble sea corals.
Mutualism between ants and fungi likely began when ants collected fungi for food, but the fungi were not essential to their survival at first. According to the researchers, the pressure from the post-impact environment may have transformed this relationship into a mutual dependence. Over time, the ants became reliant on fungi as their main food source, while the fungi depended on the ants for sustenance and reproduction.
Rodrigues explained that four groups of ants today cultivate four types of fungi. In some cases, ants even manipulate fungal growth to produce nutrient-rich structures. "When we cultivate them in the lab, the fungi take the expected form of hyphae. However, inside the colony, one of these hyphae types becomes swollen and forms structures similar to grape clusters, rich in sugars. We still don't know how the ants do this," said Pepijn Wilhelmus Kooij, a researcher at IB-UNESP and co-author of the study.
Mauricio Bacci Junior, another co-author, noted that the rise of fungus farming likely provided ants with a reliable food source at a time when other resources were scarce. The ants' cultivation of fungi allowed them to survive in changing environments, including the expansion of the Cerrado biome 27 million years ago. This diversification ultimately led to the evolution of modern leafcutter ants.
The study's findings also suggest that the enzymes produced by ant-cultivated fungi have significant biotechnological potential. These enzymes, which are highly effective at breaking down organic matter, are now being studied for applications such as plastic degradation.
Research Report:Asteroid impact may have turned ants into fungus farmers 66 million years ago
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