The frequency and diversity of maternally inherited endosymbionts in solitary bees of North America

Solitary bees play an important role as pollinators of crops and flora. Certain species are utilized for orchard pollination, making them desirable for commercial use in North America. Due to the expanding use of bees within the genera Megachile and Osmia in commercial orchards, these bees are sold and shipped nationwide to supply demands. This flux of bees also means movement of their microbiota. Some bacteria residing in bees include endosymbionts capable of causing reproductive anomalies. Translocated bees could influence local bees if individuals from different regions have different endosymbiont infections. For example, presence of bacteria that induce cytoplasmic incompatibility, which results in inviable offspring from matings between infected males and uninfected females, could cause pollinator declines. However, parthenogenesis-inducing bacteria could propagate populations of bees for commercial use. To test for presence of bacteria capable of reproductive manipulation in commercially available species of orchard pollinating bees in the United States, I used diagnostic PCR to screen for 5 bacterial species previously documented to cause reproductive anomalies. I also screened wild-caught solitary bees from Lexington (KY) to compare with the commercial bees. I found a negligible frequency of endosymbiont infection in the commercial bees, with a single individual, Osmia cornifrons being infected by Wolbachia. However, I found a strikingly high frequency of Wolbachia infection in locally caught bees within the family Halictidae. I also found visible pathogens in some commercial bees, indicating that endosymbiotic bacteria may not be the only factor influencing local pollinators, and commercial shipments could infect local bees.