Enhancer activity linked to social variation across populations of a socially flexible bee

Gene regulatory changes influence the evolution of many morphological traits, but their role in behavioral evolution is less clear. Comparative genomics studies of social insects suggest that changes in gene regulation are associated with evolutionary transitions in social behavior, but the activity of predicted regulatory regions has not been tested empirically. We used STARR-seq, a high-throughput enhancer discovery tool, to identify and measure the activity of enhancers in the socially flexible sweat bee, Lasioglossum albipes. We identified over 30,000 enhancers in the L. albipes genome from three social and three solitary populations. Strikingly, only 12% of enhancers were active in all populations, while 40% of enhancers were population-specific, suggesting extensive variation and rapid divergence in regulatory regions of L. albipes. In addition, we identified 1537 enhancers with significant differences in activity between social and solitary populations, with proximal genes enriched for Gene Ontology terms related to neuron projection, axon choice point recognition, and photoreceptor development. Combining enhancer activity with population genetics data of the same populations revealed a subset of differential enhancers with signatures of selection associated with social behavior, and also identified variants associated with differences in enhancer activity. Together, these results provide the first empirical map of enhancers in a socially flexible bee and highlight links between cis-regulatory variation and activity associated with social behavior.