COLLABORATIVE RESEARCH: What makes a generalist herbivore? The interplay between top-down and bottom-up forces on herbivore diet breadth

地球上三分之一的物种是以植物为食的昆虫(食草动物)，它们是环境健康的关键。例如，昆虫食草动物是其他动物的食物，如鸟类、蛇和哺乳动物。昆虫食草动物为开花植物授粉，但它们也可能是粮食作物的害虫，这会减少我们的食物供应。因此，为了保护自然栖息地和我们的食物供应，我们必须知道昆虫食草动物是如何受到它们的食用植物和吃它们的动物的影响的。经过几十年的研究，我们仍然不知道为什么昆虫食草动物以特定的植物为食。尽管很少有食草昆虫是以多种不同植物为食的多面手，但多面手是最具破坏性的农作物害虫。这项研究将研究一种常见的多面手食草动物来回答：是什么允许多面手食草动物使用新植物或以许多不同类型的植物为食？回答这个问题是了解害虫何时以及如何传播到不同作物上的关键。这个项目将教育小学生、初中生、高中生和大学生。这个项目将为低收入家庭的初中女生建立一个科学夏令营。生物学中尚未解决的主要问题之一是理解为什么会有这么多不同的物种。昆虫食草动物是这个问题的理想研究群体，因为它们是如此多样化。寄主植物的利用是昆虫食草动物多样化的重要驱动力，然而，大多数研究考察了饮食广度和昆虫食草动物进化之间的联系，主要集中在专业食草动物上。专注于专家并不能告诉我们哪些因素导致食草动物专门化或保持通用性。通过关注多面手，这个项目将研究寄主植物的使用和天敌的选择性力量如何导致食物的扩张或收缩，从而影响昆虫食草动物的进化和多样化。使用一种以400多种植物为食的多面手食草动物(秋季网虫，美国白蛾)，这个项目将：1)确定食物广度是种群还是个体水平的特征，并使用候选基因方法测试食物广度的遗传基础；2)调查是否通过食物广度预测局部对寄主植物的适应；3)测试天敌的组成和丰度如何影响食草动物的食物广度；4)测试从天敌逃逸是否解释了劣质宿主的食物扩张；以及5)研究寄主植物和天敌的选择力量如何随着时间的推移而改变。这项研究将为选择性力量如何影响多面手食草动物和饮食广度进化提供急需的测试。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

One-third of all species on Earth are insects that eat plants (herbivores) and they are key to environmental health. For example, insect herbivores are food for other animals, such as birds, snakes, and mammals. Insect herbivores pollinate flowering plants, however they can also be pests of food crops which can reduce our food supply. Thus, to conserve natural habitats and our food supply, we must know how insect herbivores are affected by their food plants and by the animals that eat them. After decades of research, we still do not know why insect herbivores feed on particular plants. Even though very few insect herbivores are generalists which feed on many different types of plants, generalists are the most damaging pests of crops. This research will study a common generalist herbivore to answer: What allows generalist herbivores to use new plants or to feed on many different types of plants? Answering this question is key for knowing when and how pests spread onto different crops. This project will educate elementary, middle, high school, and college students. A science camp for middle school girls from low income families will be established by this project.One of the major unresolved questions in biology is to understand why there are so many different species. Insect herbivores are an ideal study group for this question because they are so diverse. Host plant use is an important driver of insect herbivores’ diversification, however, most studies examining the link between diet breadth and insect herbivore evolution focus on specialist herbivores. Focusing on specialists does not tell us which factors lead herbivores to specialize or to maintain generalism. By focusing on generalists, this project will study how selective forces from host plant use and natural enemies can lead to diet expansion or contraction, and thereby affect the evolution and diversification of insect herbivores. Using a generalist herbivore (fall webworm, Hyphantria cunea) that feeds on over 400 plant species across a wide geographic range, this project will: 1) Determine whether diet breadth is a population or individual-level trait, and test for the genetic basis of diet breadth using a candidate gene approach; 2) Investigate if local adaption to host plants is predicted by diet breadth; 3) Test how natural enemy composition and abundance affect herbivore diet breadth; 4) Test if escape from natural enemies explains diet expansion to poor quality hosts; and 5) Examine how the interplay of selective forces from host plants and natural enemies may change over time. This research will provide critically needed tests of how selective forces influence generalist herbivores and diet breadth evolution.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.