Floral and Foliar Source Affect the Bee Nest Microbial Community
Managed pollinators such as the alfalfa leafcutting bee, Megachile rotundata, are essential to the production of a wide variety of agricultural crops. These pollinators encounter a diverse array of microbes when foraging for food and nest-building materials on various plants. To test the hypothesis that food and nest-building source affects the composition of the bee-nest microbiome, we exposed M. rotundata adults to treatments that varied both floral and foliar source in a 2 × 2 factorial design. We used 16S rRNA gene and internal transcribed spacer (ITS) sequencing to capture the bacterial and fungal diversity of the bee nests. We found that nest microbial communities were significantly different between treatments, indicating that bee nests become inoculated with environmentally derived microbes. We did not find evidence of interactions between the fungi and bacteria within our samples. Furthermore, both the bacterial and fungal communities were quite diverse and contained numerous exact sequence variants (ESVs) of known plant and bee pathogens that differed based on treatment. Our research indicates that bees deposit plant-associated microbes into their nests, including multiple plant pathogens such as smut fungi and bacteria that cause blight and wilt. The presence of plant pathogens in larval pollen provisions highlights the potential for bee nests to act as disease reservoirs across seasons. We therefore suggest that future research should investigate the ability of bees to transmit pathogens from nest to host plant.
KeywordsSolitary bees Microbial communities ITS sequencing 16S rRNA gene sequencing
The authors would like to thank the UC Riverside Genomics Core facility staff for their Next-Generation Sequencing expertise.
This research was supported by fellowships from the National Aeronautics and Space Administration MIRO Fellowships in Extremely Large Data Sets (Award No: NNX15AP99A) and the United States Department of Agriculture National Institute of Food and Agriculture (NIFA) Predoctoral Fellowship (Award No. 2018-67011-28123) to Jason A. Rothman. Funds were also awarded to Quinn S. McFrederick from the Alfalfa Pollinator Research Initiative and NIFA Hatch (Award No. CA-R-ENT-5109-H).
Compliance with Ethical Standards
Conflict of Interest
The authors declare that they have no competing interests.
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