Genomic status of the Eurasian curlew Numenius arquata : estimating Essential Biodiversity Variables and selection signals for a declining migratory bird

The Eurasian curlew (Numenius arquata) is facing severe population declines across Europe, with Ireland experiencing an alarming decline of over 90% over the past 40 years. Despite the importance of genomic data in informing conservation strategies, current knowledge of curlew population genetics is limited. To fill this gap, researchers generated whole-genome resequencing data for 56 curlews from Ireland, Britain, and Sweden.

The study revealed minimal interpopulation differentiation between Irish and British populations, but both were distinct from the Swedish population. This differentiation was evident through principal component analysis, admixture analyses, and F ST calculations. Genetic diversity measures, including nucleotide diversity, heterozygosity, and Watterson's θ, were similar across all populations.

However, Ireland and Britain exhibited slightly elevated Tajima's D and F ROH values compared to Sweden, which could be indicative of recent population declines.

The researchers identified candidate genes that may have been subject to local selection. These genes are involved in metabolic processes, the immune response, and are potentially linked to unique migratory behaviors and environmental adaptations. These findings suggest that the impacts of population decline on genomic diversity and structure may not be immediately apparent, with potential genomic effects detectable following substantial population contractions.

Furthermore, the study demonstrated that highly migratory species, like the Eurasian curlew, can exhibit differentiation in traits relevant to their ecology. This differentiation might be driven by their strong site fidelity to specific breeding and migration sites. The findings highlight the need to consider these genomic insights in translocation planning and broader conservation strategies for this declining migratory bird.