DISSERTATION RESEARCH: Molecular Systematics and Evolution in Castilleja and Subtribe Castillejinae (Orobanchaceae).

了解杂交在创造植物物种中所起的作用，以及它对理解进化关系的影响，对于理解生物多样性的起源至关重要。杂交，或不同物种的杂交，通常会产生一种模式，在这种模式中，杂交物种表现出两个亲本物种之间的特征。如果杂交在一个物种群中很常见，由于物种的许多区别特征重叠，可能很难区分物种。更复杂的是，由于重叠字符的相似模式，最近起源的物种可能很难区分。要确定导致相似模式的这些不同历史进程的重要性，首先需要重建物种之间的遗传关系模式(“家谱”)。主要分布于北美西部的卡斯蒂利亚属(印度画笔属)由约180种组成，是解决这些问题的合适模式。初步结果表明，卡斯蒂利亚属是从一组关系密切的一年生物种进化而来的，其中大多数物种是多年生的。这与人们普遍认为的一年生植物是从多年生祖先进化而来的观点相矛盾。然而，在南美洲已经发现了一年生刷物种的少量辐射，但对这些植物的研究很少，它们与其他卡斯蒂利亚物种的关系尚不清楚。因此，这项研究的目标有三个方面：1)建立一个得到良好支持的、物种水平的进化树，描述卡斯蒂利亚属物种之间的关系；2)确定最近的物种辐射与杂交在创造卡斯蒂利亚属内重叠特征的观察模式方面的重要性；以及3)调查南美洲一年生卡斯蒂利亚属物种与该属其他物种的关系。这些目标将通过首先从其原生范围内采集约120个卡斯蒂利亚物种，然后比较采样物种之间的几个DNA序列来实现。使用计算机算法比较DNA序列并推断该群体的进化历史，就有可能测试可能对卡斯蒂利亚物种形成起作用的进化过程的重要性。所获得的结果不仅将有助于理解物种丰富群体的多样化模式，而且还将有助于理解植物物种形成过程中的一些主要过程。已完成和正在进行的研究将在美国植物学会、美国植物分类学家学会和系统生物学学会的年度科学会议上报告。将为更广泛的植物学和科学界以及正在进行的生命之树项目开发一个关于卡斯蒂利亚分类和生物学的网站。拟议研究的结果将提交科学期刊发表，这项研究的结果将被纳入即将进行的卡斯蒂利亚对北美植物群的治疗。

Understanding the role that hybridization plays in creating plant species, and its impact on understanding evolutionary relationships is of vital importance to understanding the origins of biodiversity. Hybridization, or the interbreeding of different species, often creates a pattern in which the hybrid species displays characteristics intermediate to the two parent species. If hybridization is common within a species group, it can be difficult to distinguish species due to overlap in many of their distinguishing characteristics. Complicating matters, species of recent origin can be difficult to distinguish, because of a similar pattern of overlapping characters. To determine the importance of these different historical processes that result in similar patterns, first requires the reconstruction of patterns of genetic relationship between species (the 'family tree'). The large genus Castilleja (Indian Paintbrush), which is made up of ~180 species distributed chiefly in western North America, is an appropriate model to address these questions. Preliminary results indicate that the Castilleja, in which the majority of the species are perennial, has evolved from a group of closely related annual species. This contradicts the commonly held wisdom that annual plants evolve from perennial ancestors. However, a small radiation of annual paintbrush species in South America has been identified, but little study has been devoted to these plants, and their relationship to other Castilleja species is unknown. Thus, the goals of this research are 3-fold: 1) develop a well-supported, species-level evolutionary tree depicting the relationships among species of Castilleja, 2) determine the importance of a recent species radiation versus hybridization in creating the observed pattern of overlapping characteristics within Castilleja, and 3) investigate the relationship of the South American annual Castilleja species with respect to the remainder of the genus. These objectives will be accomplished by first sampling ~120 Castilleja species from their native ranges, and then comparing several DNA sequences between the sampled species. Using computer algorithms to compare the DNA sequences and extrapolate the evolutionary history of the group, it is possible to test the significance of the evolutionary processes that may have been instrumental to speciation in Castilleja. Results obtained will contribute not only to the understanding of patterns of diversification in species-rich groups, but also towards an understanding of some major processes involved in plant speciation. Completed and ongoing research will be reported at annual scientific meetings of the Botanical Society of America, American Society of Plant Taxonomists, and the Society for Systematic Biology. A website on Castilleja taxonomy and biology will be developed for the greater botanical and scientific community, as well as for the ongoing Tree of Life project. Results from the proposed research will be submitted to scientific journals for publication, and the results of this research will be incorporated into the upcoming treatment of Castilleja for the Flora of North America.