Phylogeny, Phylogeography, and Genetic Differentiation in California Calochortus (Liliaceae)

加州 Calochortus（百合科）的系统发育、系统发育地理学和遗传分化

• 批准号: 0444705
• 负责人: Thomas Givnish
• 金额: $ 44.99万
• 依托单位: University of Wisconsin-Madison
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2005
• 资助国家: 美国
• 起止时间: 2005-02-15 至 2009-01-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0444705&HistoricalAwards=false
• 关键词: Phylogeny; Phylogeography; Genetic; Differentiation; California

The plant genus Calochortus (Liliaceae family, with ca 60 species) has a center of diversity in California and has undergone striking diversification in flower form and habitat. Several species are restricted to small areas, and 25% occur on serpentine soils. An analysis of mutational differences in chloroplast DNA indicates that Calochortus is composed of seven geographically cohesive groups, with closely related species often having adjoining ranges. Three of the major floral forms ("cat's ears," "star tulips," for example) have arisen two to six times each, and serpentine tolerance has evolved at least seven times. It is hypothesized that such geographic cohesion and parallel radiations are the products of restricted gene flow, which should promote genetic differentiation and speciation at small spatial scales; different lineages may evolve similar adaptations as they invade different areas independently. To test these ideas, Prof. Givnish and his students will analyze the relationship of Calochortus species in the San Francisco Bay Area to each other and to landforms they occupy, using nuclear DNA variation, studies of incipient mating barriers as a function of geographic and genetic distance, and reconstruction of past patterns of migration, hybridization, and gene flow within and among species. Their objectives are to (1) reconstruct the history of geographic differentiation within the Bay Area Calochortus and determine whether the species restricted to serpentine are each other's closest relatives or have instead been derived independently from one or more of the wide-ranging species; (2) examine the role of hybridization and introgression in this complex group; and (3) analyze the pattern of genetic differentiation within a "ring-species" complex that surrounds California's Central Valley, to identify suture zones (areas of abrupt genetic differentiation) where expanding and gradually differentiating populations finally abutted each other.The proposed research will bridge traditional concerns of taxonomy, systematics, population genetics, and historical biogeography by quantifying the spatial scales at which genetic differentiation and incipient mating barriers arise within species, and relating these to the geographic and morphological patterns of divergence among species. Findings will provide the basis for comparative analyses involving other plant and animal groups in California, including ongoing research on several groups of plants and amphibians, and a ring-species complex involving the California valley oak. Data on patterns of genetic variation and differentiation will be of value to conservation. This project will train two female Ph.D. students in molecular phylogenetics, phylogeography, population genetics, and plant systematics. Prof. Givnish will recruit two undergraduates from underrepresented minorities to assist in data collection and develop senior theses. A web site on Calochortus evolution will be developed to bring results and new insights to a broad audience of amateur naturalists, conservationists, and professional botanists and evolutionary biologists.

百合科花属（Calochortus）植物约60种，在加州是一个多样性中心，其花型和生境经历了显著的多样化。有几个物种仅限于小面积，25%出现在蛇纹石土壤中。对叶绿体DNA突变差异的分析表明，Calochortus由七个地理上有凝聚力的群体组成，密切相关的物种通常具有相邻的范围。三种主要的花型（例如“猫耳”、“星星郁金香”）各出现了两到六次，而蛇纹草的耐受性至少进化了七次。据推测，这种地理凝聚力和平行辐射的产品，限制基因流，这应该促进遗传分化和物种形成在小的空间尺度;不同的谱系可能会演变成类似的适应，因为它们独立地侵入不同的地区。为了验证这些想法，Givnish教授和他的学生将分析Calochortus物种在旧金山弗朗西斯科湾区的相互关系，以及它们所占据的地形，使用核DNA变异，作为地理和遗传距离的函数的初期交配障碍的研究，以及过去迁移，杂交和物种内和物种间基因流动模式的重建。他们的目标是（1）重建海湾地区Calochortus的地理分化的历史，并确定是否限制到蛇的物种是彼此的近亲，而是独立于一个或多个广泛的物种;（2）检查杂交和渐渗在这个复杂的群体中的作用;以及（3）分析围绕加州中央谷的“环形物种”复合体内的遗传分化模式，来识别缝合带（突变遗传分化区）扩大和逐渐分化的种群最终相互融合。拟议的研究将弥合传统的分类学，系统学，种群遗传学和历史地理学，通过量化物种内出现的遗传分化和早期交配障碍的空间尺度，并将这些与物种间分歧的地理和形态模式联系起来。调查结果将提供比较分析的基础，涉及其他植物和动物群体在加州，包括正在进行的研究，对几组植物和两栖动物，和一个环种复杂的涉及加州谷橡树。遗传变异和分化模式的数据将对保护有价值。 该项目将培养两名女博士。分子生物遗传学、生物地理学、种群遗传学和植物系统学的学生。Givnish教授将从代表性不足的少数民族中招募两名本科生，以协助收集数据和撰写高级论文。将开发一个关于Calochortus进化的网站，为广大业余博物学家、自然资源保护主义者、专业植物学家和进化生物学家带来成果和新见解。