Molecular adjustment to a social niche: Brain transcriptomes reveal divergent influence of social environment on the two queen morphs of the ant Temnothorax rugatulus

In this study, we experimentally disentangled the effect of queen morph and social organization by using a full-factorial design. We expected macrogynes to be well adapted to the situation of being the only queen in a colony, whereas for microgynes, this could be an unusual and potentially stressful social environment. Conversely, we predicted that macrogynes might respond to the lower level of care potentially provided in polygynous societies compared to microgynes, for whom polygyny is the typical social organization (Negroni et al., 2021). We focus here on the transcriptional activity in the brain, as the central nervous system is where information about the social environment is perceived, processed, and can lead to physiological or behavioral responses (Manfredini et al., 2022; Jernigan & Uy 2023). There is evidence that behavioral dynamics between workers and queens depend on queen morph, as trophallactic interactions with microgynes are much more frequent (Negroni et al., 2021). In addition to changes in the expression of behavioral genes, we were interested in whether the queens responded to their social environment by altering the expression of genes associated with stress, fertility, or lifespan functions. We also investigated the influence of queen form and behavioral task on brain transcriptome of workers to determine whether T. rugatulus workers from macrogynous colonies differ in brain activity and potentially behavior from those raised and living in microgynous societies.