The gut microbiome, single nucleotide polymorphisms, and differentially expressed genes promote aggression in an ant

Animals frequently display aggressive behaviour, for example, when competing for food. Aggression is influenced by various extrinsic and intrinsic factors such as temperature, the microbiome, and genetics. However, we currently lack understanding what factors cause an animal to start aggression. Here, we use an ant species to test if chemical, microbiome, genomic, and/or transcriptomic traits correlate with the start of aggression and the reactions to it, that is, reacting aggressively or peacefully. We found nine bacterial operational taxonomic units, mutations in two genes, and eight differentially expressed genes, which were positively or negatively associated with the start of aggression or reactions to it. These traits are mainly linked to hormone signalling and neurological and synaptic functions. The results indicate that multiple traits, possibly acting in concert, affect the start of aggression and reactions to it. We speculate that such traits could promote aggression and could thus play important evolutionary roles.