Trade-offs between immunity and competitive ability in fighting ant males
Metzler S, Kirchner J, Grasse AV, Cremer S. Trade-offs between immunity and competitive ability in fighting ant males. bioRxiv, 10.1101/2023.01.30.526206.
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Abstract
Background: Fighting disease while fighting rivals exposes males to constraints and tradeoffs during male-male competition. We here tested how both the stage and intensity of infection with the fungal pathogen Metarhizium robertsii interfered with fighting success in Cardiocondyla obscurior ant males. Males of this species have evolved long lifespans during which they can gain many matings with the young queens of the colony, if successful in male-male competition. Since male fights occur inside the colony, the outcome of male-male competition can further be biased by interference of the colony’s worker force.
Results: We found that severe, but not yet mild, infection strongly impaired male fighting success. In late-stage infection, this could be attributed to worker aggression directed towards the infected rather than the healthy male and an already very high male morbidity even in the absence of fighting. Shortly after pathogen exposure, however, male mortality was particularly increased during combat. Since these males mounted a strong immune response, their reduced fighting success suggests a trade-off between immune investment and competitive ability already early in the infection. Even if the males themselves showed no difference in the number of attacks they raised against their healthy rivals across infection stages and levels, severely infected males were thus losing in male-male competition from an early stage of infection on.
Conclusions: Males of the ant C. obscurior have evolved high immune investment, triggering an effective immune response very fast after fungal exposure. This allows them to cope with mild pathogen exposures without cost to their success in male-male competition, and hence to gain multiple mating opportunities with the emerging virgin queens of the colony. Under severe infection, however, they are weak fighters and rarely survive a combat already at early infection when raising an immune response, as well as at progressed infection, when they are morbid and preferentially targeted by worker aggression. Workers thereby remove males that pose a future disease threat by biasing male-male competition. Our study thus revealed a novel social immunity mechanism how social insect workers protect the colony against disease risk.
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2023-01-31
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bioRxiv
Acknowledgement
This project received funding from the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme (grant agreement No 771402 to SC). The funding body had no role in the design of the study and collection, analysis, and interpretation of data and in writing the manuscript.
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Metzler S, Kirchner J, Grasse AV, Cremer S. Trade-offs between immunity and competitive ability in fighting ant males. bioRxiv. doi:10.1101/2023.01.30.526206
Metzler, S., Kirchner, J., Grasse, A. V., & Cremer, S. (n.d.). Trade-offs between immunity and competitive ability in fighting ant males. bioRxiv. Cold Spring Harbor Laboratory. https://doi.org/10.1101/2023.01.30.526206
Metzler, Sina, Jessica Kirchner, Anna V Grasse, and Sylvia Cremer. “Trade-Offs between Immunity and Competitive Ability in Fighting Ant Males.” BioRxiv. Cold Spring Harbor Laboratory, n.d. https://doi.org/10.1101/2023.01.30.526206.
S. Metzler, J. Kirchner, A. V. Grasse, and S. Cremer, “Trade-offs between immunity and competitive ability in fighting ant males,” bioRxiv. Cold Spring Harbor Laboratory.
Metzler S, Kirchner J, Grasse AV, Cremer S. Trade-offs between immunity and competitive ability in fighting ant males. bioRxiv, 10.1101/2023.01.30.526206.
Metzler, Sina, et al. “Trade-Offs between Immunity and Competitive Ability in Fighting Ant Males.” BioRxiv, Cold Spring Harbor Laboratory, doi:10.1101/2023.01.30.526206.
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