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

9411869模式生殖系统的巨大多样性是高等植物的一个显著特征。自交不亲和性是一种防止两性植物通过自花授粉受精的遗传系统，是促进高等植物异交的多种机制之一。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，其生理和分子基础一直是人们广泛研究的焦点。自交不亲和性在高等植物的进化中也起着重要作用。自交不亲和性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，尽管有大量关于主要生态和遗传因素的文献，但这些因素有利于自我和健康。异交受精，对自交不亲和起源或丧失的具体因素知之甚少。这两种关系密切的一年生植物的同时出现为研究自交不亲和与交配系统进化之间的关系提供了一个机会。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：小花莲花是自交不亲和的，而未被描述的共生物种是自交受精。在比较这两个物种的一些生态和遗传方面时，拟议的研究将解决自交不亲和的功能意义，重点放在这一现象的独特特征上。例如，虽然高等植物的许多机制阻止了自交，但自交不亲和是独一无二的，因为它也可能阻止近亲之间的交配。这一点的进化意义将被研究。这项研究的另一个重点将是自交不亲和性与影响柱头上自交不亲和花粉沉积的形态花特征之间的关系。从这项研究中获得的信息将有助于我们理解影响自交不亲和性丧失的因素，自交不亲和性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.