The Genetics of Dimorphism and Reproduction in Plant Populations

种群进化的特点是在促进变化的因素和对这种变化施加的遗传限制之间取得平衡。在本研究中，在雌雄异株种群中，两性之间的形态差异（两性二态性状）的进化被用作研究这种平衡的模型系统。两性二态性状的进化涉及雄性和雌性生殖性能之间的遗传权衡。这种权衡是两性之间遗传相关性的结果，这反过来反映了两性的相应特征，如花的大小，在多大程度上受到相似的遗传影响的控制。在之前的资助期内，我们对雌雄异株植物白丝兰的雌雄进行了萼径和花数的性别特异性选择，以评估这些性状在被选择性别中的遗传基础和在另一性别中的相关反应。这项工作产生了一些种群，其中男性要么变得更像男性，要么变得更像女性，以及一系列类似的具有女性特征的种群。这项研究的主要目的是从这些不同的品种中选取雄性（或雌性），将它们置于半自然环境中，并评估它们的比较生殖表现。因此，有可能评估修改这些性状对雄性或雌性植物的影响，并通过分别评估它们的雌性或雄性亲属的表现，来确定非直接选择下性别对选择的相关反应的遗传后果。这项工作将有助于我们全面了解两性二态性状的进化动力学以及两性之间遗传相关性的影响。

The evolution of populations is characterized by a balance between factors acting to promote change and genetic constraints imposed on such change. In the present study, the evolution of morphological differences between the sexes (sexually dimorphic traits) within dioecious populations is being used as a model system to investigate this balance. The evolution of sexually dimorphic traits involves genetic tradeoffs between male and female reproductive performance. Such tradeoffs are the result of genetic correlations between the sexes, which in turn reflect the extent to which corresponding traits in the two sexes, such as flower size, are controlled by similar genetic influences. In the previous funding period, males and females of the dioecious plant Silene alba were subjected to sex-specific selection for calyx diameter and flower number to evaluate both the genetic basis for these traits in the sex under selection and to assess correlated response in the other sex. This work has generated populations in which males have become either more extremely male-like or more female-like, and a similar series of populations for female traits. The primary objective of the proposed study is to take males (or females) from these different lines, place them in a semi-natural environment, and evaluate their comparative reproductive performance. Thus it will be possible to evaluate the consequences of modifying such traits in either male or female plants, and by evaluating performance of their female or male relatives, respectively, to determine the genetic consequences of correlated response to selection in the sex not under direct selection. This work will contribute to our overall understanding of the evolutionary dynamics of sexually dimorphic traits as well as the affects of genetic correlations between the sexes.