Biogenic amines shift during the pre-reproductive to reproductive transition in the small carpenter bee, Ceratina calcarata

Abstract

The shift from solitary to social living is a major evolutionary transition for social insects. In bees, this transition is marked by certain females becoming reproductive and reducing their role in nest and offspring care, duties that are assumed by other females. Biogenic amines play a significant role in regulating these behaviors in both solitary and social insects. How has the function of biogenic amines in solitary insects been coopted for social behaviors? Here, we used Ceratina calcarata, a behaviorally well-studied small subsocial carpenter bee to explore how biogenic amines may play a role in the reproductive shift over a season. We found that as females transition from a pre-reproductive to reproductive state, ovarian development is accompanied by an increase in brain levels of octopamine and serotonin. For comparison, we provide the first characterization of biogenic amines in the brains of males. These results suggest the essential role of biogenic amines in the transition of reproductive states in a bee on the brink of sociality and provide a deeper understanding of how biogenic amines may have influenced the evolution of social behavior.