DISSERTATION RESEARCH: Defensive chemistry underlying latitudinal patterns in plant-herbivore interactions

论文研究：植物与食草动物相互作用中纬度模式的防御化学

• 批准号: 1701602
• 负责人: Douglas Schemske
• 金额: $ 1.58万
• 依托单位: Michigan State University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2017
• 资助国家: 美国
• 起止时间: 2017-06-01 至 2018-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1701602&HistoricalAwards=false
• 关键词: DISSERTATION; RESEARCH; Defensive; chemistry; underlying

The distribution of crop pests is not constant in all places always. If scientists could predict where or when pests would be worst, it could prevent financial losses. This project will provide direct insight into the specific role of the environment (climate, summer length, etc.) on pest pressure. The researchers will address this question in a wild plant species rather than a crop species. This is because pesticides and agricultural practices hide the influence of natural factors. The focal species in this study is pokeweed (and associated pests). Pokeweed is a culturally significant perennial plant native to the eastern USA. Prior research has shown that pokeweed is heavily eaten by caterpillars in the southern vs. northern US. This proposal checks if pokeweed's defenses against insects are stronger in the South. That pattern would suggest that the plants in the South have adapted to a long history of stronger pest pressure. In addition, the research will answer basic questions about how the environment influences relationships between plants and insects. It will also help to address the long-standing mystery of why ecosystems closer to the equator have more species than ecosystems at higher latitudes. The project will also enhance K-12 education through the creation of videos on latitudinal diversity for distribution to teachers.This project tests the hypothesis that plants are better chemically defended at lower latitudes. The researchers will use a generalist caterpillar (Spodoptera exigua) to bioassay defense, and correlate caterpillar performance with leaf traits. Preliminary trials show that mortality is greater for S. exigua raised on a diet of pokeweed leaves from lower vs. higher latitude plants, suggesting that low-latitude plants are better defended. Lower latitude leaves are tougher, so to disentangle mechanical and chemical defense traits, ground leaves will be incorporated into agar for bioassays that test the effects of chemical defenses only. Liquid and Gas Chromatography Mass Spectrometry will characterize leaf chemistry profiles, and the ratio of carbon to nitrogen will serve as an index of leaf nutritional value. In sum, the project asks which leaf traits predict caterpillar performance over a latitudinal gradient, advancing our understanding of geographic variation in plant defense and addressing recent controversy about the generality of stronger biotic interactions at lower latitudes.

农作物害虫的分布并不总是一成不变的。如果科学家能够预测何时何地虫害最严重，就可以防止经济损失。该项目将提供对环境（气候，夏季长度等）的具体作用的直接洞察。害虫的压力研究人员将在野生植物物种而不是作物物种中解决这个问题。这是因为农药和农业做法掩盖了自然因素的影响。本研究的重点物种是美洲商陆（及相关害虫）。美洲商陆是一种具有重要文化意义的多年生植物，原产于美国东部。先前的研究表明，美洲商陆是严重吃毛毛虫在美国南部与北方。这项建议检查美洲商陆对昆虫的防御是否在南方更强。这种模式表明，南方的植物已经适应了长期以来更强的虫害压力。此外，这项研究还将回答有关环境如何影响植物和昆虫之间关系的基本问题。它还将有助于解决长期存在的谜团，即为什么靠近赤道的生态系统比高纬度的生态系统拥有更多的物种。该项目还将通过制作向教师分发的纬度多样性录像来加强K-12教育，该项目检验了低纬度植物更好地进行化学防护的假设。研究人员将使用一种多面手毛虫（Spodoptera exigua）来生物测定防御能力，并将毛虫的表现与叶片性状相关联。初步试验表明，S.甜菜上提出的饮食美洲商陆叶从低纬度与高纬度植物，这表明低纬度植物更好地保护。低纬度的叶子更坚韧，因此为了解开机械和化学防御特性，将地面叶子掺入琼脂中进行生物测定，仅测试化学防御的影响。液相色谱和气相色谱质谱将表征叶片的化学特征，碳氮比将作为叶片营养价值的指标。总而言之，该项目询问哪些叶片性状预测毛虫在纬度梯度上的表现，推进了我们对植物防御地理变异的理解，并解决了最近关于低纬度地区更强生物相互作用的普遍性的争议。