Dissertation Research: Self-incompatibility and Pollination in Two Species of Linanthus

生殖系统的多样性是高等植物的一个显著特征。在雌雄同体植物中，自交不亲和是一种阻止自交花粉受精的遗传系统，是促进高等植物异交的众多机制之一。据估计，它存在于超过一半的被子植物物种中。这一现象对植物育种具有重要意义，因此其生理和分子基础已成为广泛研究的焦点。自交不亲和在高等植物的进化中也起着重要的作用。自交不亲和的丧失和自交的进化被认为是许多被子植物家族共同的进化模式。然而，尽管有大量文献表明主要的生态和遗传因素有利于自我vs。在异交受精中，对自交不亲和性产生或丧失的具体因素知之甚少。两种密切相关的一年生植物在Linanthus属中的共存为研究自交不亲和与交配系统进化之间的关系提供了机会。这两个物种在生态和形态上是相似的，但它们的繁殖系统是不同的：Linanthus parviflorus是自交不亲和的，而一个未描述的同域种是自交受精的。在比较这两个物种的一些生态和遗传方面，拟议的研究将解决自交不亲和的功能意义，重点关注这种现象的独特特征。例如，虽然高等植物的许多机制阻止了自交受精，但自交不亲和是独特的，因为它也可能阻止近亲之间的交配。我们将对其进化意义进行研究。研究的另一个重点将是自交不亲和与影响花粉在柱头上沉积的形态花性状之间的关系。从本研究中获得的信息将有助于我们理解影响自交不亲和丧失的因素，这是高等植物交配系统进化过程中的一个关键转折点。

9411869 Schemske The great diversity of reproductive systems is a distinctive feature of higher plants. Self-incompatibility, a genetic system that prevents fertilization by self-pollen in hermaphroditic plants, is one of a number of mechanisms that promote outcrossing in higher plants. It is estimated to be present in over half of all angiosperm species. This phenomenon has important implications for plant breeding, and as a result its physiological and molecular bases have been the focus of extensive research. Self- incompatibility also plays an important role in the evolution of higher plants. The loss of self-incompatibility and evolution of selfing is thought to be a common evolutionary pattern in a number of angiosperm families. Yet despite an extensive literature on the major ecological and genetic factors favoring self-vs. cross fertilization, little is know about the specific factors involved in the origin or loss of self-incompatibility. The co-occurrence of two closely related annuals in the genus Linanthus presents an opportunity to investigate the relationship between self-incompatibility and mating system evolution. The two species are ecologically and morphologically similar, yet they are distinguished by their breeding systems: Linanthus parviflorus is self-incompatible, while an undescribed sympatric species is self- fertilizing. In comparing a number of ecological and genetic aspects of the two species, the proposed research will address the functional significance of self-incompatibility, focussing on unique features of the phenomenon. For instance, while a number of mechanisms of higher plants prevents self-fertilization, self- incompatibility is unique in that it also may prevent mating between close relatives. The evolutionary significance of this will be investigated. Another focus of the research will be the relationship between self-incompatibility and morphological floral characters that influence the deposition of se lf-pollen on the stigma. Information gained from this study will contribute to our understanding of the factors that influence the loss of self- incompatibility, a critical turning point in the course of mating system evolution in higher plants.