DISSERTATION RESEARCH: Plant toxicity at the top of a tropical mountain

植物和其专业食草动物之间的“化学军备竞赛”的特点是植物防御和昆虫食草动物的高度多样性，并适应这些防御，被认为是生物多样性的驱动力。在热带辣椒植物中新发现的植物毒素Piper Kelleyi被专门生长在这种植物上的毛虫消耗和代谢。这些化学物质对所有其他昆虫都是有毒的，特别是在光线较强的环境中。这项研究将定量衡量植物毒素的丰度和多样性如何对不同的光照强度做出反应，并将记录专门的毛虫如何因植物化学的差异而进化。该研究策略将遗传学和有机化学的最新进展与有关植物-昆虫相互作用的重要生态学问题联系起来。该项目将加强研究生教育，并将通过与当地K-12学生、教师和一个国际合作者小组的互动项目来促进科学教育。除了深入了解生物多样性的起源外，记录植物化学变化对相互作用的营养水平的影响也为药理学和农业提供了有用的数据。本论文的研究将为研究植物次生代谢物如何对热带生物多样性的起源和维持做出重要贡献。这项工作使用最近发现的热带林下灌木Piper kelleyi(胡椒科)的次生代谢物来检验与共同进化理论相关的特定假说。这些化合物会发生二聚化，在较高的光照下毒性更大，可被EOIS属的专业几何毛虫消耗和代谢，但它们对通才来说是非常有毒的。使用该模型系统检验的假设包括：1)如果在不同的寄主植物种群中发现不同的植物化学图谱，这些植物化学图谱可以作为草食动物的隔离机制，以及2)这些隔离机制导致专业草食动物的物种形成。光照强度将被操纵，以量化它们对种内植物化学变化的影响，种群基因组学技术将为专业毛虫对这些化合物的解毒进行局部适应测试。该项目还将为研究生提供机会，他们将通过与当地K-12学生、教师以及由化学家和生物学家组成的国际团队的互动项目来促进科学教育。

The "chemical arms race" between plants and their specialist herbivores is characterized by high diversities of both plant defenses and insect herbivores with adaptations to those defenses, and is considered to be a driving force of biodiversity. The newly discovered plant toxins in the tropical pepper plant, Piper kelleyi, are consumed and metabolized by caterpillars that specialize on this plant. These chemicals are toxic to all other insects, especially in higher light environments. The research will quantitatively measure how the abundance and diversity of plant toxins respond to different light intensities and will document how specialized caterpillars evolve in response to differences in plant chemistry. The research strategy links the most recent advances in genetics and organic chemistry with important ecological questions about plant-insect interactions. The project will enhance graduate education and will promote science education through interactive projects with local K-12 students, teachers, and an international group of collaborators. In addition to providing insight into the origins of biodiversity, documenting the effects of variation in plant chemistry on interacting trophic levels provides data that could be useful for pharmacology and agriculture.The dissertation research will provide a significant contribution to studies of how plant secondary metabolites contribute to the origin and maintenance of biodiversity in the tropics. The work examines specific hypotheses relevant to coevolutionary theory using the recently discovered plant secondary metabolites of the tropical understory shrub, Piper kelleyi (Piperaceae). These compounds, which dimerize and are more toxic at higher light levels, are consumed and metabolized by specialist geometrid caterpillars in the genus Eois but they are very toxic to generalists. The hypotheses tested using this model system include: 1) if distinct phytochemical profiles are found in different host plant populations, these can function as isolating mechanisms for herbivores, and 2) these isolating mechanisms lead to speciation of specialist herbivores. Light intensities will be manipulated to quantify their effects on intraspecific phytochemical variation, and population genomics techniques will provide tests for local adaptation of detoxification of these compounds by specialist caterpillars. The project will also provide opportunities for the graduate student, who will promote science education through interactive projects with local K-12 students, teachers, and an international team of chemists and biologists.