Phylogenetics and Evolution of Crassula (Crassulaceae)

景天属（景天科）的系统发育和进化

• 批准号: 0344883
• 负责人: Mark Mort
• 金额: $ 28.96万
• 依托单位: University of Kansas Center for Research Inc
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2004
• 资助国家: 美国
• 起止时间: 2004-02-01 至 2008-01-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0344883&HistoricalAwards=false
• 关键词: Phylogenetics; Evolution; Crassula; Crassulaceae

The jade plants (Crassula, Crassulaceae) are a group of approximately 200 species of flowering plants that are largely confined to South Africa. These plants, while best known for their highly fleshy leaves, display a great diversity of growth forms, ranging from annuals to long-lived shrubs and trees. Species in this group also display a spectacular diversity of flowers; some species possess tiny star-shaped flowers while others have large tubular flowers. Also noteworthy is the high diversity of chromosome numbers that have been reported for some species of jade plants; however, the significance of this variation has yet to be investigated comprehensively. In South Africa, jade plants occur in many different habitats, with many found on moist cliff faces, whereas others are confined to coastal sand dune habitats. In certain areas of the country (e.g. the Succulent Karoo Desert) these species form a major ecological component of the vegetation. Despite their ecological importance and high level of morphological diversity, the taxonomy of these plants has yet to be studied comprehensively. The proposed research by Dr. Mark Mort of the University of Kansas, with colleagues in South Africa, focuses on this attractive and complex group of plants and has several major goals: 1) Evolutionary relationships among species of jade plants will be determined through comparison of DNA sequences from multiple gene regions. This study will result in a necessary framework for examining the diversity in growth form, flowers, and chromosome numbers. In combination, this will permit an assessment of the boundaries of species within this group of plants and ultimately will assist in determining how many species should be recognized. 2) Floral diversity will be assessed via detailed measurements of approximately 17 morphological traits from field-collected flowers. This will provide important insights into floral change in this genus. 3) The extent of chromosome diversity in jade plants will be documented by conducting extensive chromosome counting. Examination of chromosome diversity in conjunction with the estimate of species relationships will permit an assessment of the importance of chromosome changes in creating the species diversity present in jade plants. South Africa, despite its relatively small size, contains a diversity of plants that is comparable to the more widely publicized tropics. Despite its uniqueness, much of the botanical diversity of this region has yet to be examined. Considering the current and ongoing threat to global biodiversity, areas of concentrated diversity, such as South Africa, require special attention. This work will contribute to graduate education at the University of Kansas and is being conducted in collaboration with botanical researchers in South Africa; the results will be communicated to educators and the general public through informal lectures in the U.S. and in South Africa.

玉植物（Crassula，景天科）是一组大约200种开花植物，主要限于南非。这些植物，虽然最有名的是它们的高度肉质的叶子，显示出巨大的多样性的生长形式，从一年生植物到长寿的灌木和树木。这一组中的物种也显示出壮观的花朵多样性;一些物种拥有微小的星形花，而另一些则拥有大的管状花。值得注意的是，一些玉植物的染色体数目的高度多样性已被报道，但这种变化的意义还有待全面调查。在南非，玉植物出现在许多不同的栖息地，许多在潮湿的悬崖表面发现，而其他仅限于沿海沙丘栖息地。在该国的某些地区（如多肉卡鲁沙漠），这些物种构成了植被的主要生态组成部分。尽管它们的生态重要性和高水平的形态多样性，这些植物的分类尚未得到全面的研究。堪萨斯大学的Mark Mort博士与南非的同事提出的研究重点是这种有吸引力的复杂植物群，并有几个主要目标：1）通过比较多个基因区域的DNA序列，确定玉植物物种之间的进化关系。这项研究将导致一个必要的框架，检查在生长形式，花和染色体数目的多样性。结合起来，这将允许评估这组植物中物种的边界，并最终将有助于确定应该识别多少物种。2)花卉多样性将通过详细测量约17个形态特征从现场采集的花朵进行评估。这将提供重要的见解花的变化，在本属。3)通过大量的染色体计数，可以了解玉石植物染色体多样性的程度。染色体多样性的检查，结合物种关系的估计，将允许在创造的物种多样性在玉石植物染色体变化的重要性进行评估。南非尽管面积相对较小，但其植物多样性可与更广泛宣传的热带地区相媲美。尽管它的独特性，这个地区的植物多样性还有待研究。考虑到全球生物多样性目前和持续面临的威胁，需要特别关注南非等生物多样性集中的地区。这项工作将有助于堪萨斯大学的研究生教育，目前正在与南非的植物学研究人员合作进行;研究结果将通过在美国和南非的非正式讲座传达给教育工作者和公众。