Rate variation in conserved noncoding DNA reveals regulatory pathways associated with social evolution

The evolution of eusociality represents an increase in complexity from individual to caste-based, group reproduction. These behavioral transitions have been hypothesized to go hand-in-hand with an increased ability to regulate when and where genes are expressed. Bees have convergently evolved eusociality up to five times, providing a powerful framework to test this hypothesis. Here, we compare conserved, non-coding sequences in eleven bee species, encompassing three independent origins of reproductive division of labor and two elaborations of eusocial complexity to examine potential links between these putatively regulatory sequences and social evolution. We find that rates of evolution in a number of these loci are correlated with social transitions, suggesting they have played a role in the evolution of these behaviors. Interestingly, loci associated with social origins represent distinct molecular pathways to those associated with subsequent elaborations. We also find many novel non-coding regions that appear to have been recruited alongside the origin of sociality in corbiculate bees; these regions are enriched for cell development and nervous system functions. Thus, our results highlight the potential importance of non-coding change in the evolution of eusociality and are consistent with the idea that regulatory innovations play a key role in insect behavioral complexity.