Genomic insights into stress response and local adaptations to climate in Willow warblers

• Applicant: Finja Strehmann
• Subject Area: Animal Physiology and Biochemistry ; Bioinformatics and Theoretical Biology ; Ecology and Biodiversity of Animals and Ecosystems, Organismic Interactions
• Term: since 2025
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 556504847

Climate change will alter the breeding conditions for birds in the future. Such changing environmental conditions can lead to increased levels of stress hormones such as corticosterone. As long-term elevated stress hormone levels can have negative effects on the breeding success of birds, it is important to modulate the activity of the adrenal cortex and thus the stress hormone levels in order to cope with unfavorable conditions without major fitness losses. In Sweden, northern and southern breeding willow warblers (recently classified as different subspecies) show different stress responses: Northern willow warblers, which face harsher conditions and shorter breeding seasons, react less strongly to handling stress than their southern conspecifics. The genetic differences between these subspecies are located on chromosomes 1, 3, and 5, with the inverted region on chromosome 3 being related to the longitude and latitude of the breeding area and thus also determining the environmental conditions during the breeding season. The aim of this study is to determine the genetic and epigenetic adaptations that are responsible for the different stress responses of the subspecies of the willow warbler. I will measure stress hormone levels using an enzyme immunoassay (EIA) to confirm the differences found in previous studies. In addition, I will conduct white blood cell counts (WBC) to determine immune adaptations related to stress, such as the ratio of heterophils to lymphocytes (H/L ratio). I will then perform a genetic analysis to determine the causes of the different stress responses. I expect to discover genetic adaptations related to the stress response as well as differences in gene expression and epigenetic changes between the two subspecies. This research will lead to a better understanding of the mechanisms underlying the different stress responses, as well as a better understanding of the adaptability of birds to environmental changes such as climate change.

• DFG Programme: WBP Fellowship
• International Connection: Sweden
• Host: Professor Dr. Staffan Bensch