Collaborative Research. Geographic Variation in Plant-Herbivore-Parasite Interactions: Self-Medication in Monarch Butterflies

寄生虫在自然界中很常见，根据定义，它们会导致宿主疾病或死亡。因此，宿主进化出了防御机制来保护自己免受寄生虫的侵害。药物的使用是一种这样的防御，在人类中是众所周知的。然而，动物是否也使用药物仍然知之甚少。黑脉金斑蝶的毛虫吃乳草植物，而一些乳草对黑脉金斑蝶寄生虫有毒。该项目将研究帝王蝶是否可以将马利筋作为一种药物，优先将卵产在有毒的马利筋上，以减少帝王蝶后代的寄生虫生长和疾病。研究人员将使用实验来测试不同类型的马利筋的药用效果，包括不同的物种和开花与非开花植物。这些实验也将被用来确定负责乳草药用特性的化学物质。该项目将进一步测试来自北美和澳大利亚四个种群的帝王蝶是否已经进化出使用乳草作为药物的能力。这些种群之间的寄生虫风险差异很大，该项目将测试寄生虫风险是否会影响帝王蝶进化出的药物行为类型。特别是，预计来自高风险人群的帝王蝶总是在药用植物上产卵（一种预防性药物），而来自低风险人群的帝王蝶只在感染时在药用植物上产卵（一种治疗性药物）。这个项目将提高我们对动物如何在自然界中对抗疾病的理解，并将强调寄生虫在动物行为进化中的作用。该项目还将把研究与教育结合起来。各级学生（高中，本科和研究生）和代表性不足的群体将参与这项工作的设计，执行和演示。研究人员还将在实验室里接待高中教师，开发用于课堂的研究项目，以加强他们的生态学和进化课程。最后，研究人员将参观帝王蝶节，向公众传授科学知识。

Parasites are common in nature and by definition cause disease or death to their hosts. As a consequence, hosts have evolved defenses to protect themselves against parasites. The use of medication is one such defense, and is well-known in humans. However, whether animals also use medication is still poorly understood. The caterpillars of monarch butterflies eat milkweed plants, and some milkweeds are toxic to monarch butterfly parasites. This project will study if monarchs can use milkweeds as a form of medication by preferentially laying their eggs on toxic milkweeds that reduce parasite growth and disease in the monarchs' offspring. The researchers will use experiments to test for the medicinal effects of different types of milkweed, including different species and flowering versus non-flowering plants. These experiments will also be used to identify the chemicals that are responsible for the milkweeds' medicinal properties. The project will further test whether monarchs from four populations in North America and Australia have evolved the ability to use milkweeds as medication. Parasite risk varies greatly between these populations, and the project will test whether parasite risk affects the type of medication behavior that monarchs have evolved. In particular, it is expected that monarchs from high-risk populations always lay their eggs on medicinal plants (a form of prophylactic medication), whereas monarchs from low-risk populations only lay their eggs on medicinal plants when infected (a form of therapeutic medication). This project will enhance our understanding of how animals fight disease in nature, and will emphasize the role of parasites in the evolution of animal behavior. The project will also integrate research with education. Students of all levels (high school, undergraduate and graduate) and from underrepresented groups will participate in the design, execution and presentation of this work. The researchers will also host high school teachers in the lab to develop research projects for use in their classes to strengthen their ecology and evolution curriculum. Finally, the researchers will visit monarch butterfly festivals to teach the general public about science.