Survival of the flexibEEL: Genomic evolution of climatic flexibility and population collapse of critically endangered freshwater eels

• Applicant: Dr. Leon Hilgers
• Subject Area: Evolution, Anthropology
• Term: since 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 530763738

Climate change threatens biodiversity, which forms a basis for human life on earth. We thus need to understand what makes species resistant to climate- and ecosystem change. While climate change increasingly favors climate generalists, the genomic basis of climatic flexibility remains unknown. Here, freshwater eels offer a unique opportunity. Recent work confirmed that temperate eel species, which thrive across diverse ecosystems from the arctic to the subtropics, form single panmictic populations. Accordingly, their remarkable climatic flexibility is not based on local adaptation of subpopulations. Additionally, temperate eels likely evolved twice convergently from tropical ancestors with narrow climatic niches. This project: flexibEEL, will investigate the evolutionary history and genomic evolution of climatic and ecological flexibility in freshwater eels. To this end, I will generate currently lacking tropical eel reference genomes, comprehensively analyze selection, gene losses and gene family evolution in freshwater eels, and integrate these results with experimental gene expression data across different temperatures and salinities. While climatic flexibility made eel populations remarkably stable for >500,000 years, the European eel population collapsed by over 90% since the 1960s. To illuminate key threats and evaluate the potential for evolutionary rescue, I will generate the first historical eel population genomic dataset. Systematic screens for allele frequency changes between historical and modern eels will identify selected alleles during the population collapse and changes of introgression from the American eel. Together, flexibEEL will provide crucial insights into the genomic basis of climatic flexibility and important information to save the commercially highly valuable, critically endangered European eel from extinction.

• DFG Programme: Research Grants