Genomic footprint of evolution of eusociality in bees: floral food use and CYPome “blooms”

Comparative analyses of genomes of ten bee species representing different degrees of social complexity have demonstrated that independent transitions to eusociality are often accompanied by or lead to expansions or contractions of gene families (albeit different families across independent lineages). Because collective gathering, processing, and storage of plant products is a hallmark of bee social complexity, we examined the genomic inventory of cytochrome P450 genes (the CYPome) in these ten genomes, to search for footprints of eusociality in phytochemical detoxification pathways and, using a Bayesian implementation of the McDonald–Kreitman test, evidence of adaptive evolution within P450 lineages associated with food processing in eusocial florivorous Bombus and Api s species versus eusocial carnivorous Polistes species.We found no patterns linking CYPome size to level of social complexity within the ten bee genomes at the gene family level; however, a pattern emerged at the subfamily level, with the CYP6AS subfamily most diverse in perennial eusocial resin-collecting bees. In Apis mellifera , several CYP6AS enzymes are known to metabolize flavonols, ubiquitous constituents of nectar and honey, pollen and beebread, and resins and propolis. CYP6AS subfamily size varies from 7 in the solitary Habropoda laboriosa and the facultatively eusocial Lasioglossum albipes to 17 in the perennial eusocial Melipona quadrifasciatus ; the degree of sociality across the ten species is correlated with CYP6AS inventory size (Spearman’s rho = 0.704, p