Symbiotic Relationships in Fungus-Growing Ant Agriculture

Fungus-growing ants of the tribe Attini have evolved a sophisticated form of agriculture in which they cultivate specialised fungal cultivars within subterranean chambers, forming what are known as fungus gardens. The ants supply fresh plant material as manure, while the fungus breaks down recalcitrant polymers into edible nutrients, notably via swollen hyphal cells called gongylidia that serve as the primary ant food source. This core mutualism is further reinforced by a third partner: antibiotic-producing Actinobacteria, often Pseudonocardia species, housed on the ant cuticle. These bacteria synthesise a suite of antifungal compounds that protect the fungal crop from specialised mycoparasites, chiefly Escovopsis. The result is a highly integrated tripartite symbiosis that has persisted for tens of millions of years, featuring co-evolutionary adaptations in ant behaviour, fungal physiology, bacterial metabolite production and pathogen counter-defences. Studies now reveal reciprocal genomic shifts in both ants and cultivars, dynamic microbial community structures in gardens and refuse, and a rich chemical ecology underpinning both mutualistic maintenance and defensive warfare.

Research from Nature Portfolio

Recent work has demonstrated that social interactions among leaf-cutting ants can inadvertently disperse synthetic fungicides, leading to complete colony mortality when toxic baits are used. Experimental assays of allogrooming, self-grooming and touch among groups of ant workers showed that a quinone-inside-inhibitor fungicide is efficiently transferred, highlighting the risk of collateral toxicity in integrated pest management programs. Foundational genomic analyses have uncovered reciprocal evolution in the ant–fungus symbiosis, revealing accelerated structural rearrangements in ant genomes alongside loss of enzyme domains in fungal cultivars as agriculture shifted towards full domestication and leaf-cutting. Complementary chemical imaging studies have mapped the spatial distribution of antimicrobial metabolites at inhibition zones between protective bacteria and the pathogen Escovopsis, identifying key compounds such as actinomycins and elaiophylins that demarcate zones of microbial warfare and emphasise the chemical dimension of colony defence.

Symbiotic Relationships in Fungus-Growing Ant Agriculture publication trend

The graph below shows the total number of articles in symbiotic relationships in fungus-growing ant agriculture across all publications each year (not limited to Nature Index journals).

Technical terms

Fungus garden: The cultivated fungal biomass within dedicated nest chambers where ants deposit plant material.

Cultivar: The domesticated fungal symbiont maintained and propagated by ant colonies.

Gongylidium: Specialized, nutrient-rich swollen hyphal cell produced by the cultivar for ant consumption.

Escovopsis: A genus of specialised mycoparasitic fungi that infects and can decimate ant fungus gardens.

Actinobacteria: A phylum of filamentous bacteria, including Pseudonocardia, that produce antifungal metabolites.

Autophagy: A cellular process of self-digestion and recycling of cytoplasmic components into new structures.

References

1. Evidence that the domesticated fungus Leucoagaricus gongylophorus recycles its cytoplasmic contents as nutritional rewards to feed its leafcutter ant farmers. IMA Fungus (2023).
2. Contamination and mortality of leaf-cutting ant workers by the quinone inside inhibitor fungicide after social interactions. Scientific Reports (2023).
3. Reciprocal genomic evolution in the ant–fungus agricultural symbiosis. Nature Communications (2016).
4. Imaging mass spectrometry and MS/MS molecular networking reveals chemical interactions among cuticular bacteria and pathogenic fungi associated with fungus-growing ants. Scientific Reports (2017).
5. From the inside out: Were the cuticular Pseudonocardia bacteria of fungus-farming ants originally domesticated as gut symbionts?. PNAS Nexus (2024).
6. Microbial Community Structure of Leaf-Cutter Ant Fungus Gardens and Refuse Dumps. PLOS ONE (2010).
7. Leucoagaricus gongylophorus Produces Diverse Enzymes for the Degradation of Recalcitrant Plant Polymers in Leaf-Cutter Ant Fungus Gardens. Applied and Environmental Microbiology (2013).
8. A mixed community of actinomycetes produce multiple antibiotics for the fungus farming ant Acromyrmex octospinosus. BMC Biology (2010).
9. Chemical warfare between fungus-growing ants and their pathogens. Current Opinion in Chemical Biology (2020).