Doctoral Dissertation Research: Multi-Scale Analysis of Gene Flow in the Emergent Aquatic Macrophyte Hymenocallis coronaria

博士论文研究：挺水水生植物 Hymenocallis coronaria 基因流的多尺度分析

• 批准号: 0401799
• 负责人: Kathleen Parker
• 金额: $ 1.2万
• 依托单位: University of Georgia Research Foundation 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: 2004-05-01 至 2007-04-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0401799&HistoricalAwards=false
• 关键词: Doctoral; Dissertation; Research; Multi; Scale

Water movement, which is the primary seed dispersal agent for many aquatic plants, is unidirectional throughout an upland drainage basin. Models of gene flow based on terrestrial environments, where seed dispersal is often multidirectional, are likely inadequate for representing patterns of gene flow in aquatic plants. Few studies have investigated the influence of unidirectional stream flow on patterns of genetic variation in aquatic plants, however, and these studies have reported contradictory results. Furthermore, gene flow both within and among populations has rarely been examined in stream environments, and many questions remain concerning how these processes function at different scales of analysis. This Doctoral Dissertation Research Improvement project will use molecular techniques to examine gene flow in Hymenocallis coronaria (shoals spider lily), an aquatic plant that occurs in shoal habitats in piedmont streams from Alabama to South Carolina but is absent from several watersheds in the middle of its range. The project's first broad objective is to examine the effects of unidirectional stream flow on genetic structure and gene flow within and among populations of Hymenocallis coronaria. Specifically, a combination of nuclear DNA and chloroplast DNA markers will be used to (1) determine whether genetic variability increases progressively downstream both within and among populations, (2) examine the influence of pollen flow vs. seed flow in stream environments, and (3) test which of three gene flow models best represents the patterns of gene flow among populations. The second broad objective is to examine the effects of habitat characteristics and land-use history on population distribution, genetic structure, and gene flow, and how these factors, in turn, affect microevolutionary processes in an aquatic macrophyte. In concert with molecular techniques, stream discharge, water temperature, turbidity, dissolved oxygen, sediment depth in the channel, shoals lithology, and strike and dip of the shoals rock units will be measured to determine (1) which factors are associated with the absence of Hymenocallis coronaria populations from the middle of the species range, (2) whether the exclusion of populations from the uninhabited drainage basins is of prehistoric origin or result from more recent human-related disturbance, and (3) whether populations in isolated drainages are at a greater risk for extinction with ongoing land-use changes.Hymenocallis coronaria is a rare plant that has a relatively restricted range in the southeastern United States. The plant is protected as a threatened or endangered species by the states of Alabama and Georgia. It is listed as imperiled by the state of South Carolina; and protection has been sought under the Endangered Species Act. Documented population extinctions have occurred due to reservoir impoundment, and populations continue to be threatened by further water resource development. In addition to providing information about gene flow in aquatic environments, this research will further basic understanding of the response of this relatively rare species to changing environmental conditions within its range. The results also will inform resource managers as they formulate policy that affects not only this particular state-level endangered botanical resource but potentially other aquatic plants throughout the region affected by the same set of disturbances. As a Doctoral Dissertation Research Improvement award, this award also will provide support to enable a promising student to establish a strong independent research career.

水分运动是许多水生植物种子传播的主要媒介，在整个高地流域是单向的。 基于陆地环境的基因流模型，种子传播往往是多向的，可能不足以代表水生植物的基因流模式。 然而，很少有研究调查了单向水流对水生植物遗传变异模式的影响，这些研究报告了相互矛盾的结果。 此外，种群内和种群间的基因流动很少在溪流环境中被研究，关于这些过程在不同尺度的分析中如何发挥作用，仍然存在许多问题。 这个博士论文研究改进项目将使用分子技术来检查基因流在Hymenocallis coronaria（浅滩蜘蛛百合），水生植物，发生在浅滩栖息地的皮埃蒙特流从亚拉巴马到南卡罗来纳州，但在其范围的中间几个流域缺席。 该项目的第一个广泛的目标是研究单向流的遗传结构和基因流的影响Hymenocallis coronaria的种群内和种群之间。 具体而言，核DNA和叶绿体DNA标记的组合将用于（1）确定遗传变异性是否在种群内和种群间的下游逐渐增加，（2）检查花粉流与种子流在溪流环境中的影响，以及（3）测试三种基因流模型中哪一种最能代表种群间的基因流模式。 第二个广泛的目标是研究栖息地特征和土地利用历史对种群分布，遗传结构和基因流的影响，以及这些因素如何反过来影响水生植物的微进化过程。 结合分子技术，将测量河流流量、水温、浊度、溶解氧、河道沉积物深度、浅滩岩性以及浅滩岩石单元的走向和倾角，以确定（1）哪些因素与物种范围中间的膜瓣花属（Hymenocallis coronaria）种群的缺失有关，（2）将人口排除在无人居住的流域之外是史前起源还是近代与人类有关的干扰的结果，以及（3）在孤立的排水系统中的种群是否有更大的灭绝风险，Hymenocallis coronaria是一种稀有植物，在美国东南部的范围相对有限。 该植物被亚拉巴马州和格鲁吉亚州作为受威胁或濒危物种保护。 它被南卡罗来纳州列为濒危物种，并根据《濒危物种法》寻求保护。 由于水库蓄水，已经发生了记录在案的人口减少，人口继续受到进一步水资源开发的威胁。 除了提供有关水生环境中基因流动的信息外，这项研究还将进一步了解这种相对罕见的物种对其范围内不断变化的环境条件的反应。 研究结果还将为资源管理者提供信息，因为他们制定的政策不仅影响这种特定的国家级濒危植物资源，而且可能影响整个地区受同一系列干扰影响的其他水生植物。 作为博士论文研究改进奖，该奖项还将提供支持，使有前途的学生建立一个强大的独立的研究生涯。