Ant Farmers

By Eryk Fisher

Something most people may take for granted is that humans have farmed and mastered agriculture over thousands of years, changing society and our species’ survival tactics forever. But what most people don’t realize is that humans are not the only creatures to do so, or even close to being the first. Although we may have developed interesting techniques and chemicals to better produce crops for sustenance, we are still not alone in this either. There are several species of ants that have developed symbiotic relationships with certain types of fungi to thrive. That’s right, ants and mushrooms living together under one roof.

Leaf-cutter ants are a widely known variety, in fact, you have likely seen a picture like this one before. But what people don’t realize is that they do not actually eat the leaves. They are unable to digest the plant material itself like most organisms on Earth, but they have made friends with someone who can. This is where fungi take over and use their specialty in decomposition to convert plant material into morsels ants feed from. This process is so vital to the ants, some species start new colonies by having the young queen take a piece of the fungus and move it to the new location! This keeps the genetic material intact for future generations and has led to the breeding of highly specialized ants and fungi that better work together.

According to researchers who followed DNA sequencing, they have tied modern-day “farmer” ants back to a common ancestor over 60 million years ago! While humans started swaying from the hunter-gatherer type of society roughly 10,000 years ago, these creatures have been mastering agriculture since the asteroid that wiped out the dinosaurs. In fact, it’s been theorized the very same asteroid is likely what caused this technique to be adopted in the first place! When little sunlight and vast amounts of decaying organic material overwhelmed Earth after the collision, this was exactly the type of climate where fungi excel. With little to eat and resources scarce, the theory is that ants adapted to work with fungi underground where it was safer. After many millions of years, we have over 200 species of ants that behave this way, some with more complex techniques than others. These techniques are referred to as low- and high-level agriculture and haven’t stopped ever since it started.

Lower agriculture is more common and uses fungi that can reproduce with other strains in the wild or be replaced in cases of emergency. High-level agriculture is where things get interesting. These ants have been farming for so long with the same fungi, it can no longer reproduce with wild fungi, otherwise known as being genetically isolated. It needs the ants to provide for it to continue reproducing, but in return, they produce gongylidia which are not found in any other fungi except within ant colonies. These gongylidia are structures of the fungi which ants consume for nutrition. The ants cannot live without this specific fungus because incidentally, living together for so long caused the ants to biologically stop producing arginine. Arginine is an amino acid crucial to building proteins and ultimately, survival.

Fortunately, the fungus provides this amino acid by decomposing the plant material ants carefully stored inside special chambers throughout their colony, using fecal matter and saliva to enhance the process. These fungi pastures are meticulously tended to and guarded by the ants, who deliberately select certain leaves to provide a specialized blend of nutrients for the fungi. Taking care of the fungus is no easy feat considering they must also control temperature, humidity, airflow, and supply specific nutrition to perpetuate the process. Surprisingly, these ants have even developed a mutualistic relationship with members of the Streptomyces bacterium found only on special sections of the ants, which produce antibiotics specifically targeting a rival parasitic fungus Escovopsis. This rival is even specially trained in targeting only the very fungus the ants wish to eat from.

All of this is a particularly amazing system of checks and balances, where all members of this ecosystem are contributing to survival even after millions of years. If only humans could develop such eco-friendly and sustainable methods of agriculture, we may slow down the ongoing pollution crisis plaguing Earth. That’s why I believe we should take notes from these apocalypse survivors and strive for the sort of balance they have achieved. Using chemicals and pollutants to care for our own farms has led to a significant level of ecological harm, not to mention building resistance in pests and more resilient pathogens which may have extending consequences we simply aren’t aware of.

 

Resources

Currie, C. R. (2001). A community of ants, fungi, and bacteria: A multilateral approach to studying symbiosis. Annual Review of Microbiology, 55(1), 357–380. https://doi.org/10.1146/annurev.micro.55.1.357

De Fine Licht, H. H., Boomsma, J. J., & Tunlid, A. (2014). Symbiotic adaptations in the fungal cultivar of leaf-cutting ants. Nature Communications, 5(1), 5675. https://doi.org/10.1038/ncomms6675

Ješovnik, A., González, V. L., & Schultz, T. R. (2016). Phylogenomics and divergence dating of fungus-farming ants (Hymenoptera: Formicidae) of the genera sericomyrmex and apterostigma. PLOS ONE, 11(7), e0151059. https://doi.org/10.1371/journal.pone.0151059

Seal, J. N., Gus, J., & Mueller, U. G. (2012). Fungus-gardening ants prefer native fungal species: Do ants control their crops? Behavioral Ecology, 23(6), 1250–1256. https://doi.org/10.1093/beheco/ars109