Ants have been domesticating cultivated crops for 50 million years, research reveals

Saturday, December 26, 2015 by: David Gutierrez, staff writer
Tags: crop domestication, ants, agriculture

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(NaturalNews) Humans have been domesticating and cultivating agricultural crops for only slightly more than 10,000 years. In contrast, species of ants have been cultivating crops for 50 million years -- so long that the ants and their crops have co-evolved to become dependent on each other, according to a study conducted by researchers from the Universities of Copenhagen and Lund and published in the journal Nature Communications.

Leaf cutter ants, found only in the Americas, are famous for harvesting fresh vegetation (leaves and flowers), then taking them back to their underground nests and using them as a base to grow a fungus that the entire colony feeds on. The new study was conducted on a particular lineage of these ants that is also known to recycle its own manure to provide fertilizer for its fungal crops.

After humans, leaf cutter ants reportedly form the largest and most complex animal societies known. A single colony can number millions of individuals.

Evolutionary leap leads to population boom

In the new study, researchers examined a particular fungal lineage cultivated by leaf cutter ants. This fungus has evolved to develop inflated filaments that grow in thick bundles, called staphylae. The researchers conducted an analysis of these staphylae, discovering that they are rich in carbohydrates, fats, enzymes and amino acids, and are capable of providing all the nutritional needs of the leaf cutter ants. Notably, the researchers discovered that the ants that grow this fungus have actually lost the ability to produce some of the essential enzymes and amino acids contained in the staphylae.

Further analysis showed that the specialized staphylae evolved between 20 and 25 million years ago, and that the ants probably lost the ability to produce nutrients contained in the staphylae at around the same time.

This evolutionary jump enabled a huge leap forward in the scale of leaf cuter societies. Although the ants had been cultivating edible fungus since about 50 million years ago, their farms had been small and had been able to sustain only small populations. After the evolution of staphylae, colonies were able to become much larger.

"Although it took ages of slow natural selection, today's ant farms are [about 100,000] times larger than those of the first ancestors that invented farming," first author Henrik De Fine Licht said.

Ants and fungus like "single organism"

Even as the ants lost the ability to synthesize certain nutrients, the fungus lost the ability to reproduce outside the ant colonies -- becoming, in effect, a single long-lived clonal organism.

The researchers believe that the tight relationship between the ants and the fungus explains a mystery of leaf cutter biology: Whereas human farming specialization and cultivation of clonal crops usually increases susceptibility to disease (such as the Irish potato famine or the current plight of banana crops), leaf cutter colonies are incredibly robust and almost never fall prey to serious disease.

"It is as if the farming ant families and their underground gardens have become single organisms where queen, nurses, foragers, brood and fungus are connected in a huge interaction network," De Fine Licht said.

"All parties make complementary contributions just like different tissues in a single body. So far studies have only looked at division of labor among the ants, but now we know that fungal organs are also of key significance. No other fungus has evolved such organs [staphylae] because they are only meaningful when you rely on farmers. This is similar to cultivated wheat varieties that no longer drop their seeds because humans only propagated lineages that allowed them to harvest the spikes rather than having to pick up the seeds one by one."

Sources for this article include:

http://plen.ku.dk

http://www.nature.com

http://ngs-expert.com

http://www.arkive.org