Development and Selection in the Correlated Evolution of Breeding System, Life History, and Physiology in Clarkia xantiana

开花植物中一个非常常见的进化现象是自花授粉繁殖系统从异交繁殖系统进化而来。与异交祖先不同，自花授粉的种、亚种或变种不依赖于传粉者的访问来成功定子。这个项目解决了两个问题。首先，一个自交分类单元与其相关的异交祖先在形态和开花时间上的差异，在结构（如花和叶）和整个植物的发育上发生了哪些变化？特别是在自交分类单元中，花的大小小，开花早，是通过加速发育或较短的发育时间实现的。第二个问题是结构和整个植物的早熟是否适应自交分类单元所占据的边缘环境。早熟被认为是有利的，因为环境压力通常与较短的生长季节有关。本研究的重点是比较异交和自花传粉的克拉拉（onagracae）的亚种。克拉拉是一种冬季一年生植物，其自花亚种发生在异交者活动范围边缘的干旱环境中。将研究这两个亚种的花和营养植物发育。在实验花园中，发育和形态特征的自然选择将沿着跨越两个亚种的一部分地理范围的降雨梯度进行测量。亚种之间的生理差异和生理选择也将被研究，因为生理是植物在逆境下生长的重要决定因素。该项目的意义在于，它解决了植物主要进化转变的一个很少被研究的方面，包括新物种的起源。此外，通过分析发育和选择在性状组合进化中的作用，该项目解决了进化生物学中的一个基本问题：为什么性状会一起进化？最后，该项目还探讨了压力环境下进化的本质，这一主题在栖息地面临人为压力和气候变化的影响时具有特别重要的意义。

9629086 Geber A very common evolutionary occurrence in flowering plants is the evolution of a self-pollinating breeding system from an outcrossing breeding system. Unlike its outcrossing ancestor, the self-pollinating species, subspecies or variety does not depend on pollinator visitation for successful seed set. This project addresses two questions. First, what changes in the development of structures (such as flowers and leaves) and of whole plants have been responsible for the differences in morphology and flowering time between a selfing taxon and its related outcrossing ancestor? In particular, is small flower size and early flowering in the selfing taxon achieved by means of an accelerated rate development or a shorter duration of development. The second question is whether early maturation of structures and whole plants is adaptive in the marginal environments occupied by the selfing taxon. Early maturation is postulated to be advantageous because environmental stress is often associated with a shorter growing season. The proposed study focuses on a comparison of the outcrossing and self-pollinating subspecies of Clarkia xantiana (Onagraceae), a winter annual in which the selfing subspecies occurs in arid environments at the margin of the outcrosser's range. Floral and vegetative plant development in the two subspecies will be examined. Natural selection on developmental and morphological characters in experimental gardens will be measured along a rainfall gradient that spans a portion of the geographic range of the two subspecies. Physiological differences between the subspecies and selection on physiology will also be examined, because physiology is an important determinant of plant growth under stress. The significance of the project is that it addresses a little-studied aspect of a major evolutionary transition in plants, including the origin of new species. In addition, by analyzing the roles of development and selection in the evolution of suites of characters, the project addresses a fundamental issue in evolutionary biology: why do traits evolve together? Lastly, the project also addresses the nature of evolution in stressful environments, a topic that has acquired particular significance as habitats are facing the impacts of anthropogenic stresses and climate change.