Genomic bases of short-term evolution in wild barn owls revealed by long-term monitoring and population-scale sequencing

Understanding how wild populations undergo rapid phenotypic evolution requires linking phenotypic change to its underlying genomic architecture over contemporary timescales. Here, we leverage a 30-year study of Swiss barn owls ( Tyto alba ) to examine long-term changes in two melanin-based traits (plumage coloration and spottiness) that have previously been linked to multiple fitness-related traits. We document a consistent temporal shift toward darker and more heavily spotted individuals and show, using whole-genome sequencing of 3,102 individuals, that these traits are controlled by a small number of loci of major effect with partially overlapping architectures. Temporal allele frequency analyses reveal subtle but consistent changes at these loci. By comparing empirical trajectories to simulations, we show that genetic drift alone is insufficient to explain the observed patterns at one major locus, indicating a role for selection. Our results demonstrate how selection acting on a small number of loci can contribute to rapid phenotypic evolution of continuous traits in the wild and highlight the value of long-term genomic and phenotypic monitoring for disentangling evolutionary processes.