Museomics Dissects e Genetic Basis for Adaptive Seasonal Coloration in e Least Weasel

Dissecting e link between genetic variation and adaptive phenotypes provides outstanding opportunities to understand fundamental evolutionary processes. Here, we use a museomics approach to investigate e genetic basis and evolution of winter coat coloration morphs in least weasels (Mustela nivalis), a repeated adaptation for camouflage in mammals wi seasonal pelage color moults across regions wi varying winter snow. Whole-genome sequence data were obtained from biological collections and mapped onto a newly assembled reference genome for e species. Sampling represented two replicate transition zones between nivalis and vulgaris coloration morphs in Europe, which typically develop white or brown winter coats, respectively. Population analyses showed at e morph distribution across transition zones is not a by-product of historical structure. Association scans linked a 200-kb genomic region to coloration morph, which was validated by genotyping museum specimens from intermorph experimental crosses. Genotyping e wild populations narrowed down e association to pigmentation gene MC1R and pinpointed a candidate amino acid change cosegregating wi coloration morph. is polymorphism replaces an ancestral leucine residue by lysine at e start of e first extracellular loop of e protein in e vulgaris morph. A selective sweep signature overlapped e association region in vulgaris, suggesting at past adaptation favored winter-brown morphs and can anchor future adaptive responses to decreasing winter snow. Using biological collections as valuable resources to study natural adaptations, our study showed a new evolutionary route generating winter color variation in mammals and at seasonal camouflage can be modulated by changes at single key genes.