Smithsonian Institution scientists compiled and analyzed an extensive genetic database, and found that some mushroom crops became completely dependent on ants 27 million years ago
When humans began growing crops thousands of years ago, agriculture had already existed for millions of years. In fact, some lineages of animals grew their own food long before man evolved as a species.
Colonies of ants began growing mushrooms when an asteroid hit Earth 66 million years ago, according to new research. This damage caused mass extinction but also created ideal conditions for fungi to thrive. Innovative ants began to grow the mushrooms, creating an evolutionary partnership that became even closer 27 million years ago and continues to this day.
In a paper published today, Oct. 3, in the journal Science, scientists from the Smithsonian's National Museum of Natural History analyzed genetic data from hundreds of species of fungi and ants to create detailed evolutionary trees. Comparing these trees allowed the researchers to create an evolutionary timeline of ant farming and identify when ants first began growing mushrooms.
"Ants have been farming and growing mushrooms long before humans existed," said entomologist Ted Schultz, the museum's curator of ants and lead author of the new paper. "We can probably learn something from the agricultural success of these ants over the last 66 million years."
Almost 250 different species of ants in the Americas and the Caribbean grow mushrooms. The researchers divide these ants into four agricultural systems based on their breeding strategies. Leafcutter ants are among those who implement the most advanced strategy known as high agriculture. These ants harvest pieces of fresh vegetation to provide food for their fungi, which in turn grow food for the ants called gongylidia. This food helps feed complex colonies of leafcutter ants that can number in the millions.
Schultz spent 35 years studying the evolutionary relationship between ants and fungi. He made more than 30 expeditions to locations in Central and South America to observe this interaction in nature and raised colonies of leaf-cutter ants and other mushroom-growing ants in his laboratory at the museum. Over the years, Schultz and his colleagues have collected thousands of genetic samples of ants and fungi from across the tropics.
This sample pool was essential to the new paper.
"To really identify patterns and reconstruct how this relationship has evolved over time, you need a lot of samples of ants and the fungi they grow," Schultz said.
The team used the samples to sequence genetic data for 475 different species of fungi (288 of which are grown by ants) and 276 different species of ants (208 of which are mushroom growers) – the largest genetic database of mushroom-growing ants ever collected. This allowed the researchers to create evolutionary trees of the two groups. Comparing wild mushroom species with their cultivated relatives helped researchers determine when ants began using certain mushrooms.
The data revealed that ants and fungi have been intertwined for 66 million years. This is about the time an asteroid hit Earth at the end of the Cretaceous period. This catastrophic collision filled the atmosphere with dust and debris, which blocked the sun and prevented photosynthesis for years. The resulting mass extinction wiped out roughly half of all plant species on Earth at the time.
However, this disaster was a blessing for the mushrooms. These organisms thrived as they consumed the abundant dead plant matter that covered the soil.
"Extinction events can be huge disasters for most organisms, but it can be positive for others," Schultz said. "At the end of the Cretaceous, the dinosaurs didn't do well, but the fungi thrived."
Many of the fungi that thrived during this period probably fed on rotting leaf litter, which brought them into close contact with ants. These insects harnessed the abundant fungi for food and continued to rely on the resistant fungi as life recovered from the extinction event.
The new work also revealed that it took nearly another 40 million years for ants to develop more advanced agriculture. Researchers have been able to trace the origin of this advanced practice to about 27 million years ago. During this time, a rapidly cooling climate changed habitats around the world. In South America, drier habitats such as scrub savannas and steppes have fragmented large areas of humid tropical forests. When ants took fungi from the humid forests to drier regions, they isolated the fungi from their original wild populations. The isolated fungi became completely dependent on the ants to survive in the dry conditions, setting the course for the more advanced farming system practiced by the leafcutter ants today.
"The ants domesticated these fungi in the same way that humans domesticated crops," Schultz said. "What's amazing is that we can now date when the more advanced ants first grew the more advanced fungi."
More of the topic in Hayadan:
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gross lie
66 million years? An atheist who misleads our people.
Nonsense at levels of damage to intelligence