Social behavior in bees influences the abundance of bacterial symbionts

We use bacterial 16S rRNA sequencing and metagenomics to identify a bacterial symbiont widespread across the bee family Halictidae with a degenerating genome, a characteristic suggestive of a soon to be obligate association. This bacterium is closely related to a variety of species in the genus Sodalis that also appear to be in the early stages of symbiosis with a diversity of insects. Similar to Wolbachia, Sodalis may specialize in establishing tight relationships with insect hosts. Remarkably, we find two strains of Sodalis within a single species of bee, though they never appear together in the same individual suggesting competition for host occupancy. Overall, we find three strains of Sodalis that have convergently evolved associations with halictids. Surprisingly, these strains of Sodalis appear to differ in abundance depending on the social behavior of their host bees.