TY - JOUR T1 - Convergent evolution of seasonal camouflage in response to reduced snow cover across the snowshoe hare range JF - bioRxiv DO - 10.1101/851766 SP - 851766 AU - Matthew R. Jones AU - L. Scott Mills AU - Jeffrey D. Jensen AU - Jeffrey M. Good Y1 - 2019/01/01 UR - http://biorxiv.org/content/early/2019/11/29/851766.abstract N2 - Determining how different populations adapt to similar environments is fundamental to understanding the limits of adaptation under rapidly changing environments. Snowshoe hares (Lepus americanus) molt into white winter coats to remain camouflaged in snowy environments. In warmer climates across a small portion of their range hares have evolved brown winter camouflage – an adaptation that may spread under climate change. We used extensive genotype, exome, and whole genome data to 1) resolve range-wide patterns of population structure and gene flow in snowshoe hares and 2) investigate the factors shaping the origins and distribution of winter-brown camouflage variation across the range. In coastal Pacific Northwest (PNW) populations, winter-brown camouflage is known to be determined by a single recessive haplotype at the Agouti pigmentation gene. Our phylogeographic analyses revealed deep historical structure and limited gene flow between PNW and more northern Boreal populations, where winter-brown camouflage is rare but widespread along the range edge. We sequenced the genome of a winter-brown Alaskan hare and show that it does not possess the winter-brown PNW Agouti haplotype, and thus represents a convergent phenotype that arose through independent mutations. However, the winter-brown PNW haplotype is present at low frequency in a distant winter-white population from Montana, consistent with a model in which strongly deleterious recessive variants spread easily across space because they are masked from selection at low frequency. Simulations show that if annual snow cover were to dramatically reduce, positive selection would likely drive the Agouti allele to eventual fixation in Montana, although the initial increase in allele frequency would be extremely slow due to the same masking effect. Our findings underscore how allelic dominance can shape the geographic extent and rate of convergent adaptation in response to rapidly changing environments. ER -