D3481: Regulatory changes underlie the transition to social behaviour in C. calcarata

Studies investigating social evolution often utilize species that are already eusocial, where presumably all of the adaptive genetic changes associated with sociality have already been completed. To fully understand eusociality, we must study species with incipient stages of social behaviour. The small carpenter bee Ceratina calcarata is an ideal model for studying the genetics and molecular biology of eusocial evolution as they can exhibit both subsocial behaviour with parental care as well as social behaviour with the help of the altruistic dwarf eldest daughter. Here, we sequenced the genomes of subsocial and social C. calcarata to identify mutations and genes associated with social behaviour and used this data to test several hypotheses related to the evolution of eusociality. We found that many genes associated with social behaviour in C. calcarata were involved in the regulation of gene expression. Many genes associated with sociality in our study were also found to significantly overlap with previous studies of differentially expressed genes associated with ‘caste-like’ behavioural states of C. calcarata. These results are consistent with both the genetic toolkit hypothesis as well as the ovarian ground plan hypothesis of eusocial evolution. Our findings clearly indicate that the earliest stages of social evolution in C. calcarata leverage existing regulatory genes and gene networks to generate new phenotypes associated with sociality.