Document Type

Article

Publication Title

Journal of Animal Ecology

Publication Date

2025

Keywords

bumblebees, cost mitigation, ecological immunology, functional immunity, microbiota

Abstract

  1. Ecological immunology posits that variation in host resistance to infection may be attributed partly to the ecological and evolutionary costs of immunity. While the deployment of immune defence is necessary to combat pathogenic infection, hosts pay energetic and other costs for activation.
  2. Host-associated beneficial microbiota have been shown to affect multiple host traits, including immunity, but how interactions with these microbial communities may mitigate the costs of immune activation remains an open question. For apid bees, including eusocial bumblebees, core members of the adult gut microbiota contribute to a variety of fitness-relevant traits and provide a key ecological and evolutionary relationship contributing to ecological success.
  3. Here we test the hypothesis that the host-associated microbiota provides benefits to bumblebee immunity, including the mitigation of the costs associated with inducible immune responses. Freshly emerged germ-free adult workers were supplemented with their native microbiota via experimental faecal transplants from nestmates or kept deprived of their native microbiota inoculum. We assessed functional measures of induced immunity and assessed the costs of non-pathogenic immune activation for survival.
  4. In support of our hypothesis, we find that microbiota supplementation strengthened functional antibacterial immunity. Moreover, although we observed a cost of immune activation for survival, the cost was much greater for bees deprived of their native gut microbiota compared to those supplemented. Thus, we provide evidence that in addition to other roles, the microbiota mitigates costs of immune deployment.
  5. This demonstrates a key role for host-associated microbiota in the realization of induced immune defence, and contributes more broadly to our understanding of microbiota-immune interactions in the context of ecological immunology.

Funding Source

We would like to thank Dr. Tom Nielsen and Dr. Kathy Bohn for their funding support for this project to Austin C. Calhoun and Ben M. Sadd, and for the Mockford-Thompson Fellowship awarded by Phi Sigma Biological Honors Society to Austin C. Calhoun for a summer fellowship. This work was further funded by the National Institutes of General Medicine Sciences of the National Institutes of Health under award number R15GM12968 to Ben M. Sadd and the U.S. Fish and Wildlife Service's Threatened and Endangered Species Template award number F22AP02271 to Ben M. Sadd. This article was published Open Access thanks to a transformative agreement between Milner Library and Wiley.

Comments

First published in Journal of Animal Ecology (2025): https://doi.org/10.1111/1365-2656.70180

Supplemental data available at https://doi.org/10.5061/dryad.ncjsxkt8v

DOI

10.1111/1365-2656.70180

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