In one of the first studies to look at the entire genome of leafcutter ants and the fungi they farm, scientists had found a surprising level of evolutionary give-and-take which tied the species together in a symbiotic relationship that could lead to their extinction if broken up.
Writing in the journal Nature Communications, the research team claims that 55 to 60 million years ago, shortly after the demise of dinosaurs, ants belonging to the tribe Attini switched from a hunter-gatherer lifestyle to subsistence farming of fungi that grew on woody plant matter – a transition that was thought to have taken place at a much later time.
While, at first, the crop was slow-growing and could sustain only tiny colonies of the pioneering “farmers”, this laid the foundation for agriculture that would eventually dwarf even human endeavours in terms of scale and efficiency.
“The ants lost many genes when they committed to farming fungi,” said study co-author Professor Jacobus Boomsma from the Smithsonian Tropical Research Institute. “It led to an evolutionary cascade of changes, unmatched by any other animal lineage studied so far.”
Over time, ants became increasingly more dependent on the domesticated fungi for nutrients – at some point even losing the capacity to feed on anything else – which, in turn, stopped producing enzymes to digest woody plant matter, making it reliant on leafy greens brought daily by the ants.
Unlike their present-day wild relatives, neither the leafcutter ants, nor their cultivar would be able to survive a significant rupture in the current predicament. In contrast to human farming, the increasing co-dependence appears to have been essential to support colonies with up to millions of ants, which are now the dominant herbivores in Neotropical forests.
In human terms, Boomsma said, the leafcutter ants’ success is akin to people figuring out how to grow a single, all-purpose, disease-, pest- and drought-resistant superfood at an industrial scale, “by the time of the ancient Greek civilization”.
To keep the 25-year-long streak of research into ants, much of which takes place in Panama through the Institute, the research team made their genome data from five ant and six fungi species publicly available.