Using Artificial Correlational Selection to Evaluate the Causes of Sexual Dimorphism

两性之间的差异在动物和植物中都很普遍。这种二形性可能是直接对一个性状进行选择的结果，也可能是性状之间的遗传相关性的结果。研究人员将检验这一假说，即由于性状之间的遗传相关性，雌雄异株植物宽叶锡兰的多个性状表现出性别差异。这一假说将通过两个数量遗传学实验进行研究。第一种方法包括一组受控杂交和随后的后代测量，以确定性状之间的遗传协方差的模式和大小。第二个实验将涉及人工选择，以调查花卉性状和生理性状之间的遗传相关性有多不稳定。他们将根据特征的组合而不是单个特征来选择改变特征之间的相关性，这是打破相关性的最有效的方法。这些实验的中心是测量和改变遗传相关性。这些相关性可能是因为多效性，即一个基因影响一个以上的性状，也可能是因为连锁，即影响性状的基因一起遗传。其中第一个是多效性，导致性状之间的长期相关性，而连锁很容易通过选择而被打破。如果研究人员无法打破性状之间的相关性，那么这将为多效性有助于遗传相关性和性别差异模式的假设提供可信的证据。

Differences between the sexes are pervasive in both animals and plants. Such dimorphism can result from selection directly on a trait or it can be a result of genetic correlations between traits. The investigators will test the hypothesis that multiple characters exhibit sex differences in the dioecious plant Silene latifolia, because of genetic correlations between traits. This hypothesis will be investigated with two quantitative-genetic experiments. The first incorporates a set of controlled crosses and subsequent measures of progeny, to determine the pattern and magnitude of genetic covariances among traits. The second experiment will involve artificial selection to investigate how labile the genetic correlations are between flower traits and physiological traits. They will select on the combination of traits rather than on individual traits to alter the correlation between traits, the most powerful way of breaking correlations.These experiments are centered on measuring and altering genetic correlations. These correlations can occur because of pleiotropy, in which one gene affects more than one trait, or because of linkage, in which the genes affecting traits are inherited together. The first of these, pleiotropy, leads to long-term correlations between traits, whereas linkage can be easily broken by selection. If the investigators are unable to break the correlation between traits, then this will lend credence to the hypothesis that pleiotropy contributes to patterns of genetic correlation and differences between the sexes.