DISSERTATION RESEARCH: The role of toxin complementation in herbivore defense

有特殊饮食的食草动物可以利用它们的食物植物中的防御性化学物质来保护自己。这项研究首次验证了食草动物也是如此，它们通过调节多种植物化学物质的摄入来优化防御敌人的能力。另外，在有毒植物中放牧可能有利于食草动物，因为它减少了过量摄入与特定食用植物物种相关的单一毒素的有害影响。这些可供选择的假设将通过三个实验来验证，这些实验涉及一种已知的毛毛虫，它会摄入一种植物毒素来防御致命的寄生虫。首先，研究人员将调查寄生和寄生虫类型如何影响毛毛虫摄入两种毒素（在不同的食物植物中发现）。其次，她将比较单独或同时摄入这两种毒素的毛毛虫对寄生虫的抵抗力。为了解决毒素稀释问题，本实验还将确定这些饲料对未寄生毛虫的生存和生长的影响。最后，她将测试未寄生的毛毛虫吃毒素的比例是否能威慑无处不在的蚂蚁捕食者。综上所述，这些结果将确定这种食草动物如何通过食用有毒植物而受益。这项工作将把药理学与动物行为和生态学联系起来。人类、家养食草动物和野生食草动物都面临着从化学成分多样化的植物性食物中获取健康饮食的共同问题。以食草毛虫为模型，这项研究将检验和发展可以应用于其他物种的科学理论，包括牲畜和人类。此外，了解食草动物选择寄主植物的原因将为管理和保护草原生物多样性提供信息，草原是濒危的生态系统，也是研究中的毛虫、植物、捕食者和寄生虫的家园。

Herbivores with specialized diets can co-opt the defensive chemicals of their food-plants for their own defense. This research provides a first test of the hypothesis that grazing herbivores do the same, by regulating their intake of multiple plant chemicals to optimize defense against enemies. Alternatively, grazing among toxic plants might benefit herbivores by reducing the harmful effects of over-ingesting a single toxin associated with a particular food-plant species. These alternative hypotheses will be tested through three experiments involving a caterpillar already known to ingest one type of plant toxin as a defense against lethal parasites. First, the researcher will investigate how parasitism and the type of parasite affect the caterpillar's intake of two types of toxins (found in different food-plants). Second, she will compare caterpillar resistance against parasites when they have consumed the two toxins singly or in combination. To address toxin dilution, this experiment will also determine the effects of these diets on the survival and growth of unparasitized caterpillars. Finally, she will test whether the ratio of toxins eaten by unparasitized caterpillars confers deterrency against ubiquitous ant predators. Taken together, these results will identify how this herbivore benefits by grazing on toxic plants. This work will connect the science of pharmacology with animal behavior and ecology. Humans, domesticated grazing herbivores, and wild grazing herbivores face the common problem of obtaining a healthy diet from a chemically diverse array of plant foods. Using grazing caterpillars as a model, this research will test and develop scientific theory that can be applied to other species, including livestock and humans. In addition, understanding the reasons for host plant selection by herbivores will inform the management and conservation of biodiversity in grasslands, which are imperiled ecosystems and home to the caterpillars, plants, predators and parasites under study.