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人如此罕见，而另一些人却如此普遍。也许有些动物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？大多数植物会产生特殊的化学物质，可以有效地防御天敌（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。这个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是如何避免被敌人淹没的。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在抵御土壤病原体方面的作用，这一点很重要，但鲜为人知。该项目的数据有可能产生新的医疗和农业应用。该项目将涉及低收入的第一代高中生和三所大学的本科生。最后，这些大学的学生将通过与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。本项目将重点研究新热带树木中常见而多样的Protium （Burseraceae）属。据推测，具有更多样化和更有效的反敌人防御的Protium物种遭受较少的密度依赖死亡率，获得强大的竞争优势，这应该转化为在当地和区域范围内更大的种群。在实验室中，代谢组学方法将与DNA测序一起评估Protium叶片和根中植物次生代谢物的多样性，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。在野外，观察和实验相结合的方法将确定这些植物-防御-敌人相互作用，并量化它们对寄主植物物种丰度的影响，以及本地和区域丰富的分类群逃避负密度依赖相互作用的能力。这一实验部分将在秘鲁伊基托斯的森林保护区进行，在那里，长期合作者和国际机构伙伴已经通过以前的国家科学基金会项目建立了永久地块。为了研究化学多样性如何影响亚马逊流域物种丰富度的大规模模式，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范围内发生变化。研究结果将为控制植物与天敌相互作用的特定化学介导机制提供关键测试，从而为高多样性热带雨林中决定稀有性和普遍性的生态过程提供一个新出现的假设。最终，这项研究将使人们更深入地了解热带森林巨大生物多样性的起源和维持背后的过程。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

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.