Comparative methods offer powerful insights into social evolution in bees

Bees are excellent models for studying the evolution of sociality. While most species are solitary, many form social groups. The most complex form of social behavior, eusociality, has arisen independently four times within the bees. Subsequent elaborations of the reproductive division of labor inherent to eusociality have led to the evolution of some of the most highly advanced forms of eusociality documented. Likewise, many reversals back to solitary behavior also create substantial variation in sociality within the bees. These replicated, independent origins and losses enable a comparative approach that facilitates the search for common mechanisms underlying transitions from solitary to group living. In this review, we discuss the extensive behavioral variation found within the bees and highlight how the comparative method has improved our understanding of social evolution. Finally, we discuss potential difficulties with this approach and outline promising avenues for future research.