Sex chromosome linked genetic variance and the evolution of sexual dimorphism of quantitative traits

Theory predicts that sex chromsome linkage should reduce intersexual genetic correlations thereby allowing the evolution of sexual dimorphism. Empirical evidence for sex linkage has come largely from crosses and few studies have examined how sexual dimorphism and sex linkage are related within outbred populations. Here we use data on an array of different traits measured on over 10,000 individuals from two pedigreed populations of birds (collared flycatcher and zebra finch) to estimate the amount of sex linked genetic variance (h2z). Out of 17 traits examined, eight showed a non-zero h2Z estimate but only four were significantly different from zero (wing patch size and tarsus length in collared flycatchers, wing length and beak colour in zebra finches). We further tested how sexual dimorphism and the mode of selection operating on the trait relate to the proportion of sex linked genetic variance. Sexually selected traits did not show higher h2Z than morphological traits and there was on...

理论预测，性染色体连锁会降低跨性遗传相关（intersexual genetic correlations），从而为性二态性（sexual dimorphism）的演化提供可能。此前有关性连锁的实证证据大多源自杂交实验，极少有研究探讨远交种群（outbred populations）中性二态性与性连锁之间的关联。本研究依托两种谱系鸟类（白领姬鹟（collared flycatcher）与斑胸草雀（zebra finch））的逾10000个个体的多性状测量数据，对性连锁遗传方差（h2z）进行了估算。在所检测的17个性状中，8个性状的h2Z估计值非零，但仅4个性状的估计值显著不为零：白领姬鹟的翼斑大小与跗跖长度，斑胸草雀的翅长及喙色。我们进一步检验了性二态性、性状所受的选择模式，及其与性连锁遗传方差占比之间的关联。经性选择（sexually selected）的性状并未表现出比形态性状更高的h2Z值，且……