The asteroid that wiped out the dinosaurs also brought opportunities for new life. Scientists have found that after the asteroid wiped out many plants, ants started farming fungi to help them survive and get the food they needed in tough times.
The meteor impact 66 million years ago created a low-light environment that allowed fungi that fed on organic matter to survive, as many plants and animals died. Additionally, the dust in the skies made it difficult for plants to undergo photosynthesis — converting light energy to make food. With the spread of fungus, researchers found it allowed fungus-farming ants to thrive in these dark times. The findings preview the start of the mutualistic relationship shared between several fungi species and ants.
“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,” says study co-author André Rodrigues, a professor at the Institute of Biosciences of São Paulo State University (IB-UNESP) in Brazil, in a media release. The study is published in the journal Science.
Researchers studied the genetic remains of 475 fungal species cultivated by ants from all over the Americas. They narrowed their focus on ultra-conserved elements of the fungal genomes. These regions stay in the genome through the evolution of a group, genetic evidence that links back to the most ancient ancestors.
“In this case, we were interested in the regions close to these elements. They show the most recent differences between species and allow us to trace a fairly accurate evolutionary line,” says study co-author Pepijn Wilhelmus Kooij, a researcher at IB-UNESP supported by FAPESP.
The genetic evidence on fungal species allowed researchers to track two distinct fungal lineages from the same ancestor of present-day leafcutter ants 66 million years ago. The study also showed the emergence of the ancestor of coral fungi, which was cultivated by ants 21 million years ago.
In the current study, researchers suggest the ancestor of the leafcutter ants lived close to fungi. The fungi may have been inside any colonies or occasionally collected for food.
Mutualism — a relationship in which both parties benefit — was forced on several fungi species and the ancestor of leafcutter ants. Researchers explain that the asteroid impact made the relationship necessary for survival, with the fungi needing ants for food and reproduction. Ants also used fungi as a significant food source.
Nowadays, four different ant groups cultivate four types of fungi. Some insects even influence how the fungi grow so they can produce certain nutrients.
“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,” Kooij explains.
The authors suggest that cultivating fungi was likely a way for ants to adapt to a nutritional shortage ants faced after the asteroid’s impact. Fungi, in turn, found it more helpful when cultivated by ants, creating a mutualistic relationship. The process goes with the fungus breaking down organic matter ants carried over. Afterward, ants eat the products made from the fungus that would not be found in other food sources at the time.
Another major event affected the future of fungus-farming ants. Ants previously lived in humid forests. However, 27 million years ago environmental changes changed the terrain to more savanna-like territories. These dry and vast areas led to more places for fungus-farming ants to roam and eventually diversify into today’s leafcutter ants.
The diversification of ants also provided an opportunity for fungi to diversify. This made them better at making food for the ants and decomposing organic matter. The way fungi evolved to decompose organic matter efficiently is now being studied as a potential way to decompose other materials like plastics.
Source: https://studyfinds.org/asteroid-dinosaurs-ants/