An asteroid wiped out the dinosaurs 66 million years ago, and caused a 15-year-long global winter that killed most life on Earth. But ants survived those harsh conditions by eating — and learning to farm — fungus. Today, 247 species of ants run fungus farms, growing and then eating the fungus. The domesticated fungus has evolved highly nutritious fruiting bodies that nourish the ants:
Some of the world’s greatest gardeners are mere millimeters long. The leafcutter ants of the Americas, for example, slice off chunks of leaves, haul them back to their nests, and feed the fresh greens to fungi, which the ants carefully tend in special climate-controlled chambers within their colonies. Just as humans can’t eat the hay we feed livestock, the ants can’t eat the leaves—only the fungi that flourish on them.
Hundreds of ant species farm fungi today, and studies of ant evolution suggest the adaptation goes back tens of millions of years. Now, scientists…pinpoint a date for the origins of the partnership and suggest a surprising catalyst: the asteroid that killed the dinosaurs 66 million years ago….Since ants’ fungal gardens were first described 150 years ago, entomologists have uncovered 247 species of ants that tend them and rely on this fungal crop to survive. Researchers surmise that the ants descend from a common ancestor that later evolved into separate species nurturing different types of fungi….
The ant and fungal taxa involved in farming both arose about 66 million years ago, which coincides with the massive asteroid strike that drove nonavian dinosaurs and many other species extinct. That cataclysmic impact produced lingering clouds of debris that shut down photosynthesis across the planet for several months, possibly even years. It was a catastrophe for most organisms, including plants and the animals that eat them—but not all. “Fungi that decompose plant material had a heyday”….Ants that had already developed a loose relationship with fungi were ready to take advantage of this newly abundant source of food…Farming evolved when plants were scarce but fungus was abundant. “Full-blown agriculture arose presumably fairly rapidly.”….
For the first few million years, the ants tended fungal species also found in the wild. Then, about 27 million years ago, a subset of ants completely domesticated their fungal cultivars, just as humans have done with most of our staples, which are now remote from their wild roots. The fully domesticated fungi include Leucoagaricus gongylophorus, the species most leafcutter ants favor for its specialized, highly nutritious fruiting bodies….As fungus-farming ants adapted to … drier conditions, they likely carried their fungi with them into new habitats. “This resulted in the fungi losing contact with their gene pools and triggered domestication, basically total dependence on their ant farmers,” Schultz says.
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