Data from: 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 only a weak
positive relationship between h2Z and sexual dimorphism. However, given
the relative scarcity of empirical studies it is premature to make
conclusions about the role sex chromosome linkage in the evolution of
sexual dimorphism.