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，寄生虫会导致宿主患病或死亡。因此，宿主进化出了防御系统，以保护自己免受寄生虫的侵袭。药物的使用就是这样一种防御，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。帝王蝶的毛虫吃马利筋植物，一些乳草对帝王蝶寄生虫有毒。该项目将研究帝王是否可以将黄花作为一种药物，优先将它们的卵产卵在有毒的乳草上，以减少帝王后代的寄生虫生长和疾病。研究人员将通过实验来测试不同类型的马利筋的药用效果，包括不同的物种以及开花和不开花的植物。这些实验还将被用来识别那些对黄花的药用特性负责的化学物质。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是否进化出将乳草用作药物的能力。寄生虫风险在这些种群之间差异很大，该项目将测试寄生虫风险是否会影响君主进化出的用药行为类型。特别是，预计来自高危种群的帝王总是在药用植物上产卵(一种预防性药物)，而来自低风险种群的帝王只有在感染时才在药用植物上产卵(一种治疗性药物)。这个项目将加深我们对动物如何与自然界中的疾病作斗争的理解，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。所有级别的学生(高中、本科生和研究生)和来自代表性不足群体的学生将参与这部作品的设计、执行和展示。研究人员还将在实验室接待高中教师，开发用于课堂的研究项目，以加强他们的生态学和进化论课程。最后，研究人员将参观帝王蝴蝶节，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.