Data from: Effect of the MC1R gene on sexual dimorphism in melanin-based colorations

Variants of the melanocortin-1 receptor (MC1R) gene result in abrupt, naturally selected colour morphs. These genetic variants may differentially affect sexual dimorphism if one morph is naturally selected in the two sexes but another morph is naturally or sexually selected only in one of the two sexes (e.g. to confer camouflage in reproductive females or confer mating advantage in males). Therefore, the balance between natural and sexual selections can differ between MC1R variants, as suggest studies showing interspecific correlations between sexual dimorphism and the rate of nonsynonymous vs. synonymous amino acid substitutions at the MC1R. Surprisingly, how MC1R is related to within-species sexual dimorphism, and thereby to sex-specific selection, has not yet been investigated. We tackled this issue in the barn owl (Tyto alba), a species showing pronounced variation in the degree of reddish pheomelanin-based coloration and in the number and size of black feather spots. We found that a valine (V)-to-isoleucine (I) substitution at position 126 explains up to 30% of the variation in the three melanin-based colour traits and in feather melanin content. Interestingly, MC1R genotypes also differed in the degree of sexual colour dimorphism, with individuals homozygous for the II MC1R variant being 2 times redder and 2.5 times less sexually dimorphic than homozygous individuals for the VV MC1R variant. These findings support that MC1R interacts with the expression of sexual dimorphism and suggest that a gene with major phenotypic effects and weakly influenced by variation in body condition can participate in sex-specific selection processes.黑皮质素1受体（melanocortin-1 receptor, MC1R）基因的变异可产生经自然选择塑造的突发性色型。若两性均受自然选择青睐某一色型，而另一色型仅在单一性别中受自然选择或性选择作用（例如为繁殖期雌性提供保护色，或赋予雄性交配优势），则此类遗传变异可能对性二态性产生差异化影响。因此，自然选择与性选择间的平衡会因MC1R变异体的不同而存在差异，已有研究显示性二态性与MC1R位点上非同义与同义氨基酸替换率之间存在种间相关性。 令人意外的是，目前尚未有研究探讨MC1R与种内性二态性的关联，以及其如何介导性特异性选择。本研究以仓鸮（Tyto alba）为研究对象，探讨了这一科学问题。该物种在红褐黑素介导的红棕色羽色程度以及黑色羽斑的数量与大小上均存在显著变异。我们发现，第126位缬氨酸（V）向异亮氨酸（I）的替换可解释三类黑色素相关颜色性状及羽毛黑色素含量中高达30%的表型变异。值得注意的是，不同MC1R基因型个体的颜色性二态性程度亦存在差异：纯合II型MC1R变异体的个体羽色红度为纯合VV型个体的2倍，而其颜色性二态性程度仅为VV型个体的2/5（即较VV型个体低2.5倍）。 本研究结果证实MC1R与性二态性的表达存在相互作用，同时表明，这类具有显著表型效应且受体况变异影响较弱的基因，可参与性特异性选择过程。