Origins and impacts of nitrogen-fixing symbioses in a major clade of flowering plants

所有生物体都需要氮来生长，但大多数物种不能直接获得大气中的氮，必须首先将其转化为适合使用的形式。豆类，如豌豆、小扁豆和大豆，以及其他几种开花植物可以与固氮细菌形成共生关系，并将它们安置在根部，以换取可用的氮。这种共生关系对于生态系统的运作和农业生产力至关重要。尽管理解这种相互作用具有很强的价值，但科学家们尚未揭示这种共生关系是如何进化的，以及它对全球开花植物多样性的长期进化后果。该项目将通过解决15，000种固氮开花植物的进化关系，分析与其细菌共生相关的基因，并将这些新知识与物种栖息地和形态特征的综合数据库联系起来，从而缩小这一差距。研究人员将通过针对高中、本科和研究生水平的生物学前沿数据科学方法研讨会来建立科学能力。对公众的宣传将提高人们对生命之树中生物共生的重要性的认识，以及对这些关系的了解如何增强粮食安全和人类福祉。研究人员将通过测试四个总体假设来评估被子植物与固氮细菌共生关系的宏观进化后果。细菌共生是否使植物物种能够侵入新的、更严酷的低氮土壤环境？如果是这样的话，是否有其他的植物特征使植物能够科普这些极端的栖息地？细菌共生体的获得是否使这些植物群体比没有这种关系的植物群体更快地进化出新的物种？地质时期的全球气候变化，包括更冷和更干燥的栖息地的扩展以及大气二氧化碳水平的下降，是否推动了细菌共生的进化？研究人员将使用ca的序列数据。230个核基因座，以重建一个时间校准的被子植物固氮进化支的系统发育框架，并开发一套生物多样性信息学方法，以产生物种分布模型和功能性状矩阵的规模。然后，研究人员将使用比较方法分析这些数据。研究的结果将提供对生态和进化因素的严格理解，这些因素推动了这种共生关系随着时间的推移而获得和损失，以及植物本身如何影响被子植物的多样化和全球分布。该项目开发的方法将促进未来的综合分析，利用丰富的，策划的数据资源，跨越广泛的系统发育，空间和时间scales.This奖项反映了NSF的法定使命，并已被认为是值得通过评估使用基金会的智力价值和更广泛的影响审查标准的支持。

All living organisms require nitrogen to grow, but atmospheric nitrogen is not directly available to most species and must first be converted into a form suitable for use. Legumes, such as peas, lentils, and soybeans, and several other flowering plant groups can form symbiotic relationships with nitrogen-fixing bacteria and house them in their roots in return for access to usable nitrogen. This symbiotic relationship is essential to ecosystem functioning and agricultural productivity. Despite the strong value in understanding this interaction, scientists have yet to unravel how this symbiosis evolved and its long-term evolutionary consequences for the global diversity of flowering plants. This project will close this gap by resolving the evolutionary relationships of 15,000 nitrogen-fixing species of flowering plants, analyzing the genes associated with their bacterial symbioses, and linking this new knowledge to a comprehensive database of species' habitat and morphological traits. Researchers will build scientific capacity through workshops on cutting-edge data science approaches in biology, targeting high school, undergraduate, and post-graduate levels. Outreach to the general public will increase awareness of the importance of organismal symbioses across the tree of life and how knowledge about these relationships can enhance food security and human well-being. Researchers will evaluate the macroevolutionary consequences of angiosperms' symbiotic relationships with nitrogen-fixing bacteria by testing four overarching hypotheses. Did bacterial symbiosis enable plant species to invade new, harsher soil environments low in nitrogen? If so, were other plant traits gained that allowed the plants to cope with these extreme habitats? Did the gain of bacterial symbioses allow these plant groups to evolve new species more rapidly than those without this relationship? Did global climate change over geologic time, including the spread of colder and drier habitats and falling atmospheric carbon dioxide levels, drive recent evolution of bacterial symbiosis? Researchers will use sequence data from ca. 230 nuclear loci to reconstruct a time-calibrated phylogenetic framework for the nitrogen-fixing clade of angiosperms and develop a suite of biodiversity informatics methods to generate species-distribution models and functional trait matrices at scale. Researchers will then analyze these data using comparative methods. Outcomes of the research will provide a rigorous understanding of the ecological and evolutionary factors that drove the gains and losses of this symbiosis through time and of how nodulation has itself impacted the diversification and global distribution of angiosperms. Methods developed by the project will facilitate future synthetic analyses utilizing rich, curated data resources across broad phylogenetic, spatial, and temporal scales.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.