Social network position is a major predictor of ant behaviour, microbiota composition, and brain gene expression

The physiology and behavior of social organisms correlates with their social environments. However, because social environments are typically confounded by age and physical environments (i.e., spatial location and associated abiotic factors), these correlations are usually difficult to interpret. For example, associations between an individual's social environment and its gene expression patterns may result from both factors being driven by age or behavior. Simultaneous measurement of pertinent variables and quantification of the correlations between these variables can indicate whether relationships are direct (and possibly causal) or indirect. Here we combine demographic and automated behavioral tracking with a multi-omic approach to dissect the correlation structure among the social and physical environment, age, behavior, brain gene expression and microbiota composition in ants. Variation in physiology and behavior were most strongly correlated with the social environment. Moreover, seemingly strong correlations between brain gene expression and microbiota composition, physical environment, age, and behavior became weak when controlling for the social environment. Consistent with this, a machine learning analysis revealed that from brain gene expression data, an individual's social environment can be more accurately predicted than any other behavioral metric. These results are consistent with the social environment being a key regulator of behavior and physiology.