Collaborative Research: Do defenses against herbivores and pathogens drive the commonness and rarity of tropical trees at local and regional scales?

亚马逊雨林是大量植物物种的家园。长期以来，科学家们一直想知道为什么有些如此罕见，而另一些如此常见。也许有些人更善于保护自己免受昆虫和疾病的侵害。这些物种可能会变得异常普遍。植物如何保护自己？ 大多数制造特殊的化学物质，可以有效防御天敌（主要是真菌和昆虫）。科学家们认为，这些化学物质可能对非常常见的物种特别重要，因为如果没有额外的保护，昆虫和真菌疾病将在密集的种群中迅速传播。该项目将测试植物化学物质是否可以解释最常见的雨林树木如何避免被敌人压倒。更一般地说，它可以解释不同地方不同物种的丰富程度。这项研究还将测试植物化学物质作为防御土壤病原体的作用，这些病原体很重要，但知之甚少。该项目的数据有可能产生新的医疗和农业应用。该项目将吸引低收入的第一代高中生和三所大学的本科生参与。最后，这些大学的学生将通过与来自秘鲁和巴西的学生一起参加热带野外生物学课程获得基本技能，并将学习如何进行雨林研究。该项目将侧重于Protium（Burseraceae），一种常见且多样的新热带树种。据推测，具有更多样和更有效的抗敌防御的Protium物种遭受更少的密度依赖性死亡率，获得了强大的竞争优势，应该转化为当地和区域规模的更大种群。在实验室中，代谢组学方法将评估Protium叶和根中植物次生代谢物的多样性，并与DNA测序相结合，以确定这些代谢物如何影响真菌病原体的存在，从而阐明它们在介导植物-天敌相互作用中的作用。在该领域，观察和实验相结合的方法将确定这些植物防御敌人的相互作用，并量化其对宿主植物物种丰度和当地和区域丰富的类群逃避负密度依赖的相互作用的能力的影响。这一实验部分将在秘鲁伊基托斯的森林保护区进行，长期合作者和国际机构伙伴已通过国家科学基金以前的项目在那里建立了永久性地块。为了调查化学多样性如何影响亚马逊流域物种丰度的大规模模式，该项目还将在秘鲁、哥伦比亚和巴西的大片地区进行系统调查，以确定化学和植物天敌群落如何在物种分布区发生变化。结果将提供一个关键的测试特定的化学介导的机制，认为控制植物-天敌的相互作用，从而确定在高多样性的热带雨林的稀有性和常见性的生态过程的一个新出现的假说。最终，这项研究将产生一个更深入的了解的过程的起源和维护的巨大的热带森林的生物多样性。这个奖项反映了NSF的法定使命，并已被认为是值得的支持，通过评估使用基金会的知识价值和更广泛的影响审查标准。

The Amazon rainforest is home to a huge number of plant species. Scientists have wondered for a long time why some are so rare and others so common. Perhaps some are better at protecting themselves from insects and diseases. These species could then become unusually common. How do plants protect themselves? Most make special chemicals that can be a potent defense against natural enemies (mostly fungus and insects). Scientists think such chemicals may be especially important in very common species because without extra protection, insects and fungal diseases would spread rapidly in dense populations. This project will test whether plant chemicals can explain how the most common rainforest trees keep from being overwhelmed by their enemies. More generally, it may explain the abundance of different species in different places. This study will also test the role of plant chemicals as defenses against soil pathogens, which are important but poorly known. Data from this project has the potential to generate new medical and agricultural applications. The project will engage and involve low income, first-generation high school students and undergraduates at three universities. Finally, students at those universities will gain essential skills by attending a tropical field biology course with students from Peru and Brazil, and will learn how to do rainforest research. This project will focus on Protium (Burseraceae), a common and diverse genus of Neotropical trees. Protium species with more diverse and effective anti-enemy defenses are hypothesized to suffer less density-dependent mortality, gaining a strong competitive advantage that should translate into larger populations at the local and regional scale. In the laboratory, metabolomic approaches will assess the diversity of plant secondary metabolites in leaves and roots of Protium in tandem with DNA sequencing to identify how those metabolites influence the presence of fungal pathogens, thus elucidating their role in mediating plant-natural enemy interactions. In the field, a combination of observational and experimental approaches will identify these plant-defense-enemy interactions and quantify their effect on host plant species abundances and the ability of locally and regionally abundant taxa to escape negative density-dependent interactions. This experimental component will be conducted in forest reserves in Iquitos, Peru where permanent plots by long-term collaborators and international institutional partners have been established through previous NSF projects. To investigate how chemical diversity might affect large scale patterns of species abundances in the Amazon basin, this project will also perform systematic surveys across large areas in Peru, Colombia and Brazil to determine how chemistry and plant natural enemy communities change across species’ ranges. Results will provide a critical test of specific chemically-mediated mechanisms thought to control plant-natural enemy interactions, and thus a newly emerging hypothesis about the ecological processes that determine rarity and commonness in high diversity tropical rainforests. Ultimately, this research will yield a deeper understanding of the processes underlying the origin and maintenance of the vast biodiversity of tropical forests.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.