Investigating the Fundamental Units of Natural Selection Amng Coral-Algal Symbioses: Ecological, Geographic, and Physiological Diversity of Host-Symbiont Genotypes

共生线虫属的线虫和甲藻结合在一起形成了地球上最重要的共生生物之一。这个项目直接和间接地解决了我们对珊瑚-藻类共生的知识中的几个主要基本差距，以及在环境干扰、污染和气候变化期间，这些伙伴关系可能如何应对严重的自然选择。对动物宿主和藻类共生体独立进行的分子遗传学研究，启发了我们对它们多样性的认识。然而，很少对这两个伴侣一起进行任何详细的研究。认识到大多数珊瑚群落中的共生生物种群似乎是克隆的，这意味着可以对完整组合的动物和藻类成分进行基因分析。“个体”级别的基因分型在最精细的遗传分辨率范围内解决了特异性和稳定性问题，并在其最基本的单位量化了“完整碱基”的多样性。通过基因分型获得的数据对于推断宿主和共生体种群之间的进化过程以及这些伙伴组合如何在面对气候变化时潜在地共同进化至关重要。事实上，这些数据最终将被用来与理论合作者一起对这些共生生物的进化模型进行参数化。认识到自然多样性在所有生态系统中的功能意义，对于了解生命是如何进化的，以及它可能如何在生态时间尺度上对气候变化做出进化反应至关重要。这项研究将调查共生生物种群的克隆多样性，这些种群与加勒比海最重要的造礁珊瑚之一--掌状顶孔珊瑚有关。这种动物对共生菌A3高度特异，尽管它的幼虫必须从环境池中获得共生体。在最近描述掌纹夜蛾种群遗传结构的工作中，对数千个样本进行了基因分型，然后存档。这些标本为深入分析共生线虫在单个群体内、具有相同动物基因(分株)的单独群体之间、在遗传上独特的群体(基因)的大型林分之间以及在整个加勒比海分布的大部分棕榈藻种群中的多样性提供了特殊的资源。基于4个可变基因座的170个样本的初步基因分型(还将开发4到8个)表明，每个群体都有一个显性克隆。这种一对一的寄主-共生体基因对应关系允许将宿主种群遗传结构与共生体遗传结构进行直接比较，以确定扩散障碍和生活史策略如何影响珊瑚和甲藻的共同进化。通过野外采集、比较生理学研究和感染实验，研究具有不同共生菌种群的不同寄主种群(库拉索岛)与共生体多样性较低(少数几个基因类型)的寄主种群(美属维尔京群岛)、以及具有低多样性共生体种群的低多样性寄主种群(佛罗里达州)之间的生态学意义、特异性和稳定性。寄主-共生体基因组合多样性的显著地理差异意味着某些种群可能比其他种群对自然选择更敏感。确定定义共生珊瑚之间相互作用的生态和进化过程对于我们基本理解珊瑚-藻类共生以及这些动物-微生物系统如何响应气候变化引发的严格选择至关重要。手掌珊瑚特别值得关注，因为它是目前被美国《濒危物种法》列为濒危物种的两个珊瑚物种之一。通过确定共生生物多样性的重要性，保护工作可以优先考虑恢复材料的来源种群。正如NOAA Acropora工作队所说，迫切需要这一信息，该项目的结果将定期公布。这里产生的数据将为杰出的理论家提供服务，使他们对这些共生生物的进化模型进行参数化，从而使更广泛的生物界和整个社会受益。这项研究包括对公共和公共机构进行教育和培训的外联任务。珊瑚-微生物相互作用的生态重要性使它们成为教授微生物和共生体对生物圈健康的重要性的有魅力的榜样。通过继续2005年以来由SECORE(性珊瑚繁殖)举办的一系列研讨会，该项目将帮助建立一个由公共水族馆和研究机构组成的合作国际网络，以建立手掌珊瑚繁殖项目。来自全国和世界各地的大型公共水族馆和动物园的科学家和专家之间的这种合作，有助于通过动物园的外联任务与公众接触，从而促进对珊瑚共生的重要性和科学基本过程的了解。研究生和本科生是该项目不可分割的一部分，他们将接受实地和实验室工作以及讲座课程方面的培训。

Cnidarians and dinoflagellates in the genus Symbiodinium combine to form one of the most important symbioses on the planet. This project addresses both directly and indirectly several major fundamental gaps in our knowledge of coral-algal symbioses, and how these partnerships may respond to severe natural selection during periods of environmental disturbance, pollution, and climate change. Molecular genetic investigations conducted independently on the animal hosts and algal symbionts have enlightened our appreciation of their diversity. However, rarely have both partners been studied together in any detail. The realization that Symbiodinium populations in most coral colonies appear to be clonal means that genotype analyses can be conducted on both the animal and algal component of an intact association. Genotyping to the level of "individual" addresses questions of specificity and stability at the finest scale of genetic resolution and quantifies the diversity of "holobionts" at its most basic unit. Data acquired through genotyping are critical for deducing evolutionary processes between host and symbiont populations and how these partner combinations are potentially co-evolving in the face of climate change. Indeed these data will ultimately be used to parameterize evolutionary models of these symbioses with theoretical collaborators. Realizing the functional significance of natural diversity in all ecosystems is vital for understanding how life evolves and how it may respond evolutionarily to climate change over ecological time scales. This study will investigate the clonal diversity of Symbiodinium populations that associate with one of the most important Caribbean reef-building corals, Acropora palmata. This animal is highly specific for Symbiodinium, A3 despite the fact that its larvae must acquire symbionts from environmental pools. In recent work describing the population genetic structure of the A. palmata, thousands of samples were genotyped for the animal and then archived. These specimens provide an exceptional resource for intensive analyses of Symbiodinium genotype diversity within an individual colony, among separate colonies with the same animal genotype (ramets), among large stands of genetically unique colonies (genets), and across populations of A. palmate throughout much of its Caribbean distribution. Initial genotyping of 170 specimens based on four variable loci (4 to 8 more will be developed) indicates that each colony harbors a single dominant clone. This one-to-one host-symbiont genotype correspondence allows for direct comparison of host population genetic structure with that of the symbiont genetic structure to identify and then model how dispersal barriers and life history strategies influence the co-evolution of corals and dinoflagellates. Field collections, comparative physiological studies, and infection experiments will be conducted to investigate the ecological significance, specificity, and stability of diverse host populations with diverse populations of symbiont (Curacao) verses diverse host populations with a low diversity (few genotypes) of symbiont (US Virgin Islands), and finally low diversity host populations with low diversity symbiont populations (Florida). Significant geographic differences in the diversity of host-symbiont genotypic combinations mean that certain populations may be more responsive to natural selection than others.Determining the ecological and evolutionary processes that define the interactions between symbiotic corals is critical to our basic understanding of coral-algal symbioses and how these animal-microbe systems may respond to severe selection induced by climate change. Acropora palmata is particularly worthy of attention because it is one of two coral species currently listed as threatened under the US Endangered Species Act. By identifying the significance of symbiont diversity, conservation efforts can prioritize source populations for restoration material. This information is urgently needed as stated by the NOAA Acropora task force and results from this project will be made available regularly. The data generated here will serve prominent theoreticians to parameterize their evolutionary models of these symbioses and thus benefit the wider biological community and society at large. This study includes outreach missions to educate and train the public and public institutions. The ecological importance of coral-microbe interactions make them charismatic examples for teaching about the importance of microorganisms and symbioses to the health of the biosphere. Through continuing a series of workshops held since 2005 by SECORE (SExual Coral REproduction), the project will help build a cooperative international network of public aquariums and research institutions to establish coral breeding programs of A. palmata. This collaboration between scientists and specialists from large public aquaria and zoos located around the nation and world, serves to engage the public through the outreach mission of the zoos and thereby promotes understanding about the importance of coral symbioses and the basic process of science. Graduate and undergraduate students are an integral part of this project and will receive training in field and laboratory work and lecture courses.