Data from: Sex-specific allelic transmission bias suggests sexual conflict at MC1R

Sexual conflict arises when selection in one sex causes the displacement of the other sex from its phenotypic optimum, leading to an inevitable tension within the genome – called intralocus sexual conflict. Although the autosomal melanocortin-1-receptor gene (MC1R) can generate colour variation in sexually dichromatic species, most previous studies have not considered the possibility that MC1R may be subject to sexual conflict. In the barn owl (Tyto alba), the allele MC1RWHITE is associated with whitish plumage coloration, typical of males, and the allele MC1RRUFOUS is associated with dark rufous coloration, typical of females, although each sex can express any phenotype. Because each colour variant is adapted to specific environmental conditions, the allele MC1RWHITE may be more strongly selected in males and the allele MC1RRUFOUS in females. We therefore investigated whether MC1R genotypes are in excess or deficit in male and female fledglings compared with the expected Hardy–Weinberg proportions. Our results show an overall deficit of 7.5% in the proportion of heterozygotes in males and of 12.9% in females. In males, interannual variation in assortative pairing with respect to MC1R explained the year-specific deviations from Hardy–Weinberg proportions, whereas in females, the deficit was better explained by the interannual variation in the probability of inheriting the MC1RWHITE or MC1RRUFOUS allele. Additionally, we observed that sons inherit the MC1RRUFOUS allele from their fathers on average slightly less often than expected under the first Mendelian law. Transmission ratio distortion may be adaptive in this sexually dichromatic species if males and females are, respectively, selected to display white and rufous plumages.性冲突（sexual conflict）指某一性别的选择作用使另一性别的表型最适值发生偏离，进而在基因组内引发不可避免的张力，即基因座内性冲突（intralocus sexual conflict）。尽管常染色体黑皮质素-1受体基因（MC1R）可在两性异色物种中诱发羽色变异，但此前绝大多数研究并未考虑MC1R可能受到性冲突影响的可能性。 在仓鸮（Tyto alba）中，MC1RWHITE等位基因与雄性典型的纯白色羽色相关联，MC1RRUFOUS等位基因则与雌性典型的深红褐色羽色相关联——尽管两性均可表达任意一种羽色表型。由于每种羽色变异均适配特定的环境条件，因此MC1RWHITE等位基因在雄性中可能受到更强的选择压力，而MC1RRUFOUS等位基因则在雌性中受到更强选择。 为此，我们探究了仓鸮雌雄幼雏的MC1R基因型频率与哈迪-温伯格预期比例相比是否存在过剩或缺失情况。研究结果显示，雄性群体的杂合子比例整体较预期低7.5%，雌性群体则低12.9%。 对于雄性个体而言，基于MC1R的选型交配的年际差异可解释各年度偏离哈迪-温伯格比例的现象；而对于雌性个体来说，杂合子比例的缺失更可用MC1RWHITE或MC1RRUFOUS等位基因的遗传概率年际变化来解释。此外，我们观察到，子代雄性从父本处继承MC1RRUFOUS等位基因的概率，平均略低于孟德尔第一定律的预期值。 若该两性异色物种的雄性和雌性分别被选择偏向表达白色与红褐色羽色，则传递比率偏倚在该物种中可能具有适应性意义。