When humans began cultivating crops hundreds of years ago, agriculture had already been around for tens of millions of years. In fact, many animal lineages have been growing their very own food long before humans evolved as a species.
Colonies of ants began cultivating fungi after they hit the bottom 66 million years ago, in response to a brand new study. This effect led to a worldwide mass extinction but in addition created ideal conditions for fungi to flourish. Innovative ants began cultivating fungi, establishing an evolutionary partnership that became much more tightly knit 27 million years ago and continues to at the present time.
In a paper published today, Oct. 3, within the journal Nature, scientists on the Smithsonian's National Museum of Natural History analyzed genetic data from lots of of species of fungi and ants to create detailed evolutionary trees. Comparing these trees allowed the researchers to create an evolutionary timeline of ant agriculture and pinpoint when ants first began cultivating the fungus.
“Ants have been doing agriculture and fungus farming for longer than humans have been around,” said entomologist Ted Schultz, curator of the Ant Museum and lead writer of the brand new paper. “We can probably learn something from the agricultural success of these ants over the past 66 million years.”
About 250 different species of ants within the Americas and the Caribbean farm fungi. The researchers organized these ants into 4 agronomic systems based on their farming strategies. Leafcutter ants are amongst those practicing a highly advanced strategy, generally known as advanced agriculture. These ants cut pieces of fresh plants to offer sustenance for his or her fungus, which in turn grows food for the ants called gongylidea. This food helps fuel complex colonies of leaf-cutter ants that may number within the tens of millions.
Schultz has spent 35 years studying the evolutionary relationship between ants and fungi. He has made greater than 30 expeditions to locations in Central and South America to watch this interaction within the wild, and has raised colonies of leafcutter and other fungus-cultivating ants in his lab on the museum. Over the years, Schultz and colleagues have collected hundreds of genetic samples of ants and fungi from across the tropics.
This collection of samples was essential to the brand new paper.
“To really detect patterns and how that association has developed over time, you need many samples of ants and their colonies,” Schultz said.
The team used the samples to sequence genetic data from 475 different species of fungi (288 of that are cultivated by ants) and 276 different species of ants (208 of that are cultivated by the fungus). . This allowed the researchers to construct evolutionary trees of the 2 groups. Comparing wild fungal species to their cultivated relatives helped researchers determine when ants began using certain fungi.
The data shows that ants and fungi have been related for 66 million years. This is across the time that an asteroid hit Earth at the tip of the Cretaceous period. The catastrophic collision filled the atmosphere with dust and debris, blocking out the sun and stopping photosynthesis for years. The resulting mass extinction worn out nearly half of all plant species on Earth on the time.
However, this disaster was a legacy for the fungus. These organisms proliferated once they ate the massive amounts of dead plant material that littered the land.
“Extinction events can be catastrophic for most organisms, but they can actually be positive for others,” Schultz said. “At the end of the Cretaceous, the dinosaurs didn't do very well, but the fungi experienced a boom.”
Many of the fungi that spread during this era likely ate up decaying leaf litter, which brought them into close contact with the ants. These insects used loads of fungi for food and continued to depend on hardy fungi as life recovered from the extinction event.
The recent work also revealed that it took about one other 40 million years for ants to develop advanced agriculture. Researchers were capable of trace the origins of this contemporary behavior to around 27 million years ago. Meanwhile, a rapidly cooling climate has modified the world's climate. In South America, dry habitats equivalent to woody savannas and grasslands broke up large areas of wet, tropical forests. When ants carried fungi from wet forests to dry areas, they separated the fungi from their wild native populations. Isolated fungi became completely depending on ants to survive in dry conditions, paving the way in which for today's advanced agricultural systems through leaf-cutter ants.
“The ants domesticated these fungi in the same way that humans domesticate crops,” Schultz said. “What's extraordinary is that we can now pinpoint the date when higher ants actually cultivated higher fungi.”
In addition to Schultz, the brand new paper includes contributions from a variety of authors related to the National Museum of Natural History, including Jeffrey Sousa-Calvo, Matthew Koskin, Michael Lloyd, Anna Jasonic and Scott E. Solomon. The study also includes authors affiliated with the University of Utah. Royal Botanic Gardens, Kew; University of California at Berkeley; US Department of Agriculture; São Paulo State University; Instituto de Investigaciones CientÃficas y Servicios de Alta TecnologÃa; Smithsonian Tropical Research Institute; University of Copenhagen; Emory University; McMaster University; Universidade Federal de Uberlandia; Arizona State University; University of Hohenheim; and Louisiana State University.
The research was supported by the US National Science Foundation; Smithsonian; University of Maryland; Louisiana State Board of Regents; Sistema Nacional de Investigación Cosmos Club Foundation; Explorers Club in Washington, DC; São Paulo Research Foundation; Brazilian Council of Research and Scientific Development; Brazilian Federal Agency for the Support and Evaluation of Graduate Education; Royal Botanic Gardens, Kew; and the Carl Zeiss Foundation.