Bacterial symbionts of sweat bees

Distribution of dN/dS ratios of free-living Sodalis (white circle), sweat bee-associated Sodalis (purple), and other insect symbionts (gray). Significance was determined by comparing to the free-living form. The sweat bee-inhabiting Sodalis appear to be experiencing widespread relaxed selection.

Several strains of bacteria in the genus Sodalis have independently colonized sweat bees and, in every case, the genomes of these bacteria appear to be experiencing relaxed selection. At least some of these strains are shared across bee species and geographic location but appear to compete with each other for territory when found together in the same individual bee. I plan to greatly expand this line of research, characterizing the Sodalis lineages inhabiting sweat bees in North America and what has predisposed this genus to repeatedly colonizing these bees. I will especially focus on the apparent competition between strains as these will likely be informative for understanding how insect-microbial symbioses stabilize over evolutionary time. Our first paper describing these findings is available on bioRxiv.