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Abstract In insects and other invertebrates, prior pathogen exposures can improve immune responses and survival to subsequent infections through immune priming. Alternatively, stress and metabolic costs of multiple infections can impair host immunity and survival. The effects of high‐temperature extremes on host–pathogen interactions are not well understood despite the increasing occurrence of heat waves caused by climate change.The response of insects to heat waves and pathogens depends on recent evolutionary history with selective pressures. Domestication of insect pests has occurred in lab colonies of model species, reducing selective pressures for immune and heat stress responses. Lab strains are often used in immunological or heat stress experiments to represent wild field strains, but the efficacy of this approach is seldom evaluated.Using the tobacco hornworm (Manduca sexta), we tested the impact of a heat wave during initial pathogen exposure on survival of a secondary infection withBacillus thuringiensisbacteria. We used a domesticated lab population and a naturally occurring field population ofM. sextato evaluate the impacts of recent domestication on immune and thermal responses.A heat wave during initial infection significantly increased survival of the secondaryB. thuringiensisinfection in the field, but not the lab population ofM. sexta.In the field population, survival of the repeated infection was temperature dependent: exposure to an initial infection event reduced survival of the secondary infection at the control temperature regime, consistent with a stress effect. However, a heat wave during the initial infection event increased survival of the secondary infection, consistent with immune priming effects.The results of this study demonstrate that (a) insect response to thermal stress and pathogens can depend on recent domestication and (b) responses of hosts to repeat pathogen exposures can be temperature‐dependent, suggesting that cross‐talk between the heat stress and immune memory pathways may have important consequences for host–pathogen outcomes under heat wave events. Read the freePlain Language Summaryfor this article on the Journal blog.
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The interactive effects of heat stress, parasitism and host plant quality in a host–parasitoid system
Abstract Species interactions are expected to change in myriad ways as the frequency and magnitude of extreme temperature events increase with anthropogenic climate change.The relationships between endosymbionts, parasites and their hosts are particularly sensitive to thermal stress, which can have cascading effects on other trophic levels.We investigate the interactive effects of heat stress and parasitism on a terrestrial tritrophic system consisting of two host plants (one common, high‐quality plant and one novel, low‐quality plant), a caterpillar herbivore and a specialist parasitoid wasp.We used a fully factorial experiment to determine the bottom‐up effects of the novel host plant on both the caterpillars' life history traits and the wasps' survival, and the top‐down effects of parasitism and heat shock on caterpillar developmental outcomes and herbivory levels.Host plant identity interacted with thermal stress to affect wasp success, with wasps performing better on the low‐quality host plant under constant temperatures but worse under heat‐shock conditions.Surprisingly, caterpillars consumed less leaf material from the low‐quality host plant to reach the same final mass across developmental outcomes.In parasitized caterpillars, heat shock reduced parasitoid survival and increased both caterpillar final mass and development time on both host plants.These findings highlight the importance of studying community‐level responses to climate change from a holistic and integrative perspective and provide insight into potential substantial interactions between thermal stress and diet quality in plant–insect systems. Read the freePlain Language Summaryfor this article on the Journal blog.
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- Award ID(s):
- 2029156
- PAR ID:
- 10543305
- Publisher / Repository:
- Wiley Online
- Date Published:
- Journal Name:
- Functional Ecology
- Volume:
- 38
- Issue:
- 3
- ISSN:
- 0269-8463
- Page Range / eLocation ID:
- 642 to 653
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript
- Journal Article:
- https://doi.org/10.1111/1365-2435.14498
