Leafcutter ants are in a chemical arms race against a behaviour-changing fungus

On the face of it, a leafcutter ant’s nest is a perfect picture of harmonious relationships. Worker ants go out to forage for fresh leaf material that they use to grow a fungus(Leucoagaricus gonglyophorous). In return for a mulchy compost of fresh leaves, the fungus breaks down the plant material to produce nutritious, edible structures which the ants can digest.

However, mine and my colleagues’ latest research suggests that this image ignores the chemical warfare being waged by leafcutter ants. In reality, they are locked in an arms race with another, parasitic fungus called Escovopsis, which plagues the ants’ food source and appears to be using chemical weapons to modify ant behaviour.

As all farmers are well aware, crops are prone to outbreaks of disease. South American leafcutter ants face a similar problem in that their fungal gardens can become infested with parasites, usually other bacterial and fungal species that feed off the nutritious fungal crop.