The domestication event affects sex-biased gene expression and evolution in duck

Genes with sex-biased expression are thought to underlie sexually dimorphic phenotypes and are therefore subject to different selection in males and females. Many have proposed that sexual conflict leads to the evolution of sex-biased expression, which resolves conflict and allows males and females to reach separate phenotypic and fitness optima. The strong selection pressures associated with domestication may cause changes in population characteristics and mating systems, which in turn can later the direction and strength of sex-specific selection. We used to compare sex-biased expression and population genomic characteristics in wild and domestic ducks (Anas platyrhynchos). We observed changes in the intensity of sexual selection by measuring sexual size dimorphism and provide an opportunity to identify the genomic divergence affected by relaxed sexual selection. Population genetic analysis shows the extent of sex-biased genes in both sexes is positively correlated with the level of both dN/dS and nucleotide diversity. This observed pattern may mainly be due to genetic constraints rather than sexual selection. We also demonstrate a clear link between domestication and sex-biased evolutionary rate in a comparative framework. Decreased polymorphism and evolutionary rate in domestication breeds generally matched life-history phenotypes known to experience artificial selection. Taken together, our work suggests the important implications of domestication in sex-biased evolution and the roles of artificial selection and sexual selection for shaping the diversity and evolutionary rate of the genome.