Sexual dimorphism in gene expression is likely to be the underlying source of dimorphism in a variety of traits. Many analyses implicitly make the assumption that dimorphism only evolves when selection favors different phenotypes in the two sexes, although theory makes clear that it can also evolve as an indirect response to other kinds of selection. Furthermore, previous analyses consider the evolution of a single transcript or trait at a time, ignoring the genetic covariance with other transcripts and traits. We first show which aspects of the genetic-variance covariance matrix, G, affect dimorphism when these assumptions about selection are relaxed. We then reanalyze gene expression data from Drosophila melanogaster with these predictions in mind. Dimorphism of gene expression for individual transcripts shows the signature of both direct selection for dimorphism and indirect responses to selection. To account for the effect of measurement error on evolutionary predictions, we estimated a G matrix for eight linear combinations of expression traits. Sex-specific genetic variances in female- and male-biased transcription, as well as one relatively unbiased combination were quite unequal, ensuring that most forms of selection on these traits will have large effects on dimorphism. Predictions of response to selection based on the whole G matrix showed that sexually concordant and antagonistic selection are equally capable of changing sexual dimorphism. In addition, the indirect responses of dimorphism due to cross-trait covariances were quite substantial. The assumption that sexual dimorphism in transcription is an adaptation is likely to be incorrect in many specific cases.

中文翻译：

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预测基因表达中性二态性的进化

基因表达中的性二态性很可能是多种性状中潜在的二态性来源。许多分析都隐含了这样一个假设，即双态性仅在选择偏爱两种性别的表型时才进化，尽管理论表明它也可以作为对其他选择的间接反应而进化。此外，先前的分析考虑了单个转录本或性状一次的演变，而忽略了与其他转录本和性状的遗传协方差。首先证明其遗传方差协方差矩阵的各个方面，G，影响异形当即将选择这些假设放宽。然后，我们牢记这些预测，重新分析果蝇果蝇的基因表达数据。单个转录本的基因表达双态性显示了双态性直接选择和对选择的间接响应的特征。为了考虑测量误差对进化预测的影响，我们估计了表达特征的八个线性组合的G矩阵。女性和男性偏爱的转录中的性别特异性遗传变异，以及一种相对无偏的组合，是非常不平等的，从而确保了对这些性状的大多数选择形式都会对二态性产生重大影响。根据整个G矩阵对选择做出的反应预测表明，性协调和拮抗选择同样能够改变性二态性。另外，由于交叉性状的协方差，二态性的间接响应是相当可观的。