Impact of heat stress on social strategies for microbial control

• Applicant: Dr. Maja Fluch
• Subject Area: Ecology and Biodiversity of Animals and Ecosystems, Organismic Interactions
• Term: since 2026
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 579858908

Animals almost continuously interact with a vast diversity of microbes, and often leverage complex strategies to promote beneficial microbial symbionts while keeping harmful pathogens at bay. In group-living animals, this balancing act is often especially demanding because social contact not only promotes the spread of pathogenic microbes among group members, but also increases the scope to transmit, and benefit from, mutualistic symbionts. Hence, group-living animals have evolved strategies of microbial control, from collective defenses against pathogens to the transmission of symbionts through trophallaxis. However, it remains little understood how robust such social strategies of microbial control are to stress caused by changing environmental conditions, including those affected by the rapid progression of anthropogenic climate change. Here, I propose research that tackles this critical issue in the burying beetle Nicrophorus vespilloides by examining how heat stress affects the expression and fitness effects of parental care and modulates its role and efficacy as a social strategy for microbial control. Burying beetles breed on carcasses of small vertebrates and are ideally suited to address this issue: they intimately interact with environmental and symbiotic microbes on their breeding resource; they show elaborate forms of parental care that are crucial to mediating these interactions; and their parenting behaviors have already been shown to be impaired under heat stress. I propose a comprehensive research program composed of four Work Packages (WPs) that will combine approaches from behavioral and chemical ecology, microbiome science, and social evolution research to answer key questions: WP1: How does heat stress impair parental microbial control? I will test how heat stress impacts the beetles' ability to "weed" the breeding resource of environmental microbes. WP2: Can parental care mitigate negative effects of heat stress? I will examine whether parental care can buffer the costs of heat stress arising from increased microbial competition. WP3: What are the interactive effects of heat and other stressors? In this WP, I will test whether the effects of heat stress on the beetle-microbe relationship are reinforced or attenuated by drought stress. WP4: Does heat stress cause long-term, transgenerational costs? In the final WP, I will examine whether heat stress impairs the social transmission of beneficial microbial symbionts from parents to offspring, leading to long-term fitness costs. Altogether, the proposed research program will make significant contributions to behavioral ecology and microbiome science by using an established insect model system to unravel the consequences of heat stress for social strategies of microbial control. In doing so, it will help understanding the potential repercussions of climate change on interactions between animals and microbes and the behaviors that animals use to control them.

• DFG Programme: WBP Position