Connecting local, regional and global scales of gene flow in planktonic marine diatoms

硅藻是普遍存在的单细胞真核生物，每年在海洋中产生约40%的固定有机碳。对硅藻物种分布和丰度与环境条件的关系的解释依赖于两个假设：(1)具有相同形态的细胞代表相同的物种；(2)被动漂流硅藻的高扩散和基因流动潜力阻碍了当地适应。最近的研究挑战了这两种假设，表明硅藻在物种内部和物种之间都具有丰富的遗传和生理变异模式。尽管在局部尺度（~100公里）上出现了种内种群分化的新证据，但通常认为浮游微生物在全球尺度上分布均匀（例如Fenchel和Finlay 2004）。目前没有关于硅藻的数据支持这一假设。除了地方尺度上有趣的数据外，对硅藻的区域和全球尺度的种群遗传学和生物地理学一无所知。这里提出的研究将集中在浮游硅藻种群在地方、区域和全球尺度上是否以及如何联系的基本问题上。种群间的连通性可以影响一个物种的生态、适应潜力、进化寿命以及最终的物种形成潜力。该研究将利用两种模式硅藻来研究当地种群如何在区域尺度上相互联系，以及区域动态如何与全球尺度的生物地理相联系。rDNA序列变异将用于测试在硅藻中观察到的广泛物种分布是否源于隐物种形成。在物种内，微卫星标记将用于鉴定遗传上不同的种群，确定它们彼此之间的关系，并检查分化的空间格局。还将研究种群间遗传分化所伴随的生理变异程度。样本将在现有海洋学和生物多样性项目的框架内收集，允许基因数据在更大的、通常是长期的研究背景下进行解释。由于对硅藻生物地理学知之甚少，这项工作将开始揭示当地和全球种群动态之间的联系。由于拟议的研究将代表硅藻种群遗传学的第一次大规模采样，它也将有助于产生许多关于调节生态过程的机制的新假设，例如在空间和时间上形成的水华，以及浮游生物中生殖隔离和最终物种形成的进化过程。更广泛的影响：拟议的研究将提供可用于新一代数值海洋生态系统模型的数据，这些模型将在全流域范围内纳入自然选择。采样将作为现有项目的一部分进行，如长期浮游生物监测、海洋生物普查和现有的海洋实地项目。该项目将以新的方式将这些项目和现有的基础设施联系在一起。研究生和高中（HS）学生教育是拟议研究的组成部分。这项拟议的研究将资助一名研究生。通过与URI海洋项目办公室（OMP）的合作，拟议的研究将包括为HS学生设计一个关于生物多样性和基因组学的解释性项目，该项目将通过Internet2远程直播、双向、工作室到教室的演示，以及视频剪辑和全国学生和教师的问答环节。OMP将协助审查教育内容，为教师提供实地测试，并使内容与国家科学教育标准保持一致。这些关键步骤将提供评估外展计划成功与否的标准。

Diatoms are ubiquitous, unicellular, eukaryotes that generate about 40% of the organic carbon fixed annually in the sea. Interpretation of diatom species distributions and abundances in relation to environmental conditions has relied on two assumptions: (1) cells with identical morphologies represent the same species and (2) high potentials for dispersal and gene flow in passively drifting diatoms prevent local adaptation. Recent studies have challenged both assumptions, suggesting diatoms possess rich patterns of genetic and physiological variation both within and between species. Although there is emerging evidence of intra-specific population differentiation on local scales (~100km), it is commonly assumed that planktonic microbes are homogenously distributed on global scales (e.g. Fenchel and Finlay 2004). There is currently no data on diatoms to support this assumption. Aside from intriguing data on local scales, nothing is known about regional and global-scale population genetics and biogeography of diatoms. The research proposed here will focus on the essential questions of if and how populations of planktonic diatoms are connected at local, regional and global scales. Connectivity among populations can influence a species'' ecology, adaptive potential, evolutionary longevity and ultimately speciation potential. The proposed research will examine how local populations are connected to each other on regional scales and how regional dynamics connect to global-scale biogeographies using two model diatom species. rDNA sequence variation will be used to test whether broad species distributions observed in diatoms result from cryptic speciation. Within species, microsatellite markers will be used to identify genetically distinct populations, determine their relatedness to each other and examine spatial patterns of differentiation. The degree of physiological variation that accompanies genetic differentiation between populations will also be examined. Samples will be collected in a framework of existing oceanography and biodiversity programs, permitting genetic data to be interpreted in the context of larger, often long-term, studies. Because little is known about diatom biogeography, this work will begin to shed light on the connections between local and global population dynamics. Because the proposed research will represent the first large-scale sampling of diatom population genetics, it will also serve to generate many new hypotheses about the mechanisms that regulate ecological processes such as bloom formation over space and time and evolutionary processes such as the development of reproductive isolation and eventual speciation in planktonic organisms. Broader impacts: The proposed research will contribute data that can be used by a new generation of numerical ocean ecosystem models that incorporate natural selection on basin-wide scales. Sampling will occur as part of existing programs such as long-term plankton monitoring, Census of Marine Life and existing oceanographic field programs. This project will tie these programs and their existing infrastructure together in new ways. Graduate and high school (HS) student education are integral components of the proposed research. The proposed research will fund one graduate student. Through a collaboration with the URI Office of Marine Programs (OMP), the proposed research will include the design of an interpretive program on biodiversity and genomics for HS students that will be delivered remotely with live, two-way, studio-to-classroom presentations coupled with video clips and Q&A sessions with students and teachers across the country via Internet2. The OMP will assist with reviews of educational content, provide field tests with teachers, and align the content to national science education standards. These critical steps will provide metrics for assessing the success of the outreach program.