Abstract
We know much about pathogen evolution and the emergence of new disease strains, but less about host resistance and how it is signaled to other individuals and subsequently maintained. The cline in frequency of black-coated wolves ( Canis lupus ) across North America is hypothesized to result from a relationship with canine distemper virus (CDV) outbreaks. We tested this hypothesis using cross-sectional data from wolf populations across North America that vary in the prevalence of CDV and the allele that makes coats black, longitudinal data from Yellowstone National Park, and modeling. We found that the frequency of CDV outbreaks generates fluctuating selection that results in heterozygote advantage that in turn affects the frequency of the black allele, optimal mating behavior, and black wolf cline across the continent. , Black wolves’ leg up In North America, wolves generally have either gray or black coats, and the proportions of these colors vary across populations. The genetics of these coat colors have been revealed, and we now know that black wolves are either homozygous or heterozygous for a gene that is also related to resistance to canine distemper virus. Analyzing data from across North America, but especially from populations in Yellowstone National Park, Cubaynes et al . found that black coats were maintained through heterozygote advantage in, and mate choice preference for, black-coated wolves in areas where canine distemper is endemic even though gray-coated wolves have higher success when the virus is absent. —SNV , Disease epidemics drive the evolution of morphology and behavior in wolves.