Gene-environment interactions in a long-lived seabird: how do immune genes and pollution interact to affect the microbiome and fitness components of common terns?

• Applicant: Professorin Dr. Sandra Bouwhuis, Ph.D.
• Subject Area: Ecology and Biodiversity of Animals and Ecosystems, Organismic Interactions
• Term: since 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 504982168

Although the environment has always been variable, anthropogenic influences are currently causing major and rapid global change. Among the predicted consequences of this change are changes in pathogen communities, as well as increases in mercury pollution. What these two environmental changes have in common, is that they are likely to affect immune system functioning, and therefore the reproductive performance as well as survival of individuals. The microbiome is the aggregate of all microbiota that reside on or within an individual’s tissues. Recent work suggests that the microbiome is affected both by the diversity at genes coding for molecules involved in the immune response, and by environmental pollution. As such, the microbiome may be a major pathway linking gene-environment interactions to fitness. Currently, however, this link can only be suggested based on results from separate lines of scientific work; a holistic study of all components is lacking. The main objective of the project we propose here therefore is to elucidate how immune gene diversity and mercury pollution interact to affect the microbiome and fitness components. We propose to do so using a longitudinal approach, by repeatedly sampling free-living common terns (Sterna hirundo) from a long-term individual based study population. Specifically, we propose to collect blood and faecal samples from individually marked terns of known sex, age and ancestry to assess their immune genotype, as well as to repeatedly assess their mercury contamination and composition of the microbiome. Moreover, we will monitor the environment (e.g. breeding density, food availability), as well as the stress levels, reproductive performance and survival of these birds. Doing so will allow us to assess within-individual changes in mercury contamination and the microbiome, the links between such changes and variation in the environment, and whether any effects on fitness components depend on immune genotype. In turn, that will allow us to test the following hypotheses: (i) Mercury contamination accumulates within individuals, increases their stress levels and reduces their microbiome diversity or affects their microbiome composition; (ii) Environmental stress (e.g. high breeding density, limited food availability) exacerbates effects of mercury contamination on individual stress levels and the microbiome; (iii) High immunogenetic diversity facilitates microbiome diversity, and mitigates effects of mercury contamination and environmental stress on individual stress levels; (iv) Gene-environment interactions affect reproductive success (assessed as the number and quality of fledglings produced) and survival (assessed as return rates).

• DFG Programme: Research Grants
• International Connection: Poland
• Cooperation Partner: Dr. Radoslaw Wlodarczyk