Collaborative Research: Understanding the Evolution of Diet Breadth through Ecoimmunology

人类商业活动和其他人为活动已经造成物种地理范围的广泛变化，影响了物种在其群落内的相互作用。由于植食昆虫占地球陆地生物量的很大一部分，了解影响它们改变饮食的因素对于预测新组织的生态系统是否以及如何运作至关重要。生态免疫学是一门新兴学科，强调免疫系统在物种相互作用和生命史特征进化中的作用。虽然植物-昆虫相互作用的研究早就认识到昆虫吃的植物种类的范围不仅取决于植物的特性，而且还取决于天敌如捕食者和寄生虫，但免疫防御在决定饮食广度方面所起的作用是一个新的研究领域。本研究探讨了一种假设，即通过增强免疫力获得的对病原体的抵抗力可以影响将新植物物种纳入昆虫食草性饮食的可能性。为了验证这一假设，研究人员将结合生态免疫学、化学生态学和微生物学的方法，使用一个由四种蝴蝶组成的模型系统，这些蝴蝶都将引进的植物车前草（车前草科）纳入它们的饮食中。研究人员将通过量化每种蝴蝶不同种群中两种常见病原体的寄生率和环境水平，评估引进植物的使用是否与疾病风险的改变有关，而每种蝴蝶种群对杉木的使用情况各不相同。在实验室中，来自这些种群的遗传资源将用于比较以杉木和祖先寄主植物物种为食的毛虫对微生物病原体的免疫反应和模拟寄生。研究人员将通过实验研究饮食、植物化学物质的吸收和居住在昆虫肠道中的细菌之间的相互作用，通过测量这些因素被操纵时的免疫反应。最后，他们将测试幼虫的感染史是否会影响产卵的雌性选择哪些植物，或者向杉木的转变是否反映了对先天宿主偏好的选择。

Human commerce and other anthropogenic activities have caused widespread changes in the geographic ranges of species, affecting how species interact within their communities. Since plant-feeding insects represent a large part of Earth's terrestrial biomass, understanding the factors that influence them to change their diets is central to predicting if and how newly organized ecosystems will function. Ecoimmunology is an emerging discipline that highlights the role of the immune system in species interactions and the evolution of life history traits. Although research in plant-insect interactions has long recognized that the range of plant species eaten by insects is shaped not only by characteristics of the plants, but also by enemies such as predators and parasites, the role played by immunological defense in determining dietary breadth is a new area of study. This research explores the hypothesis that resistance to pathogens attained via enhanced immunity can affect the likelihood of incorporating new plant species into insect herbivore diets. To test this hypothesis, researchers will combine approaches from ecoimmunology, chemical ecology and microbiology, using a model system of four butterfly species, all of which have incorporated the introduced plant, Plantago lanceolata (Plantaginaceae), into their diets. Researchers will assess whether the use of the introduced plant is associated with altered disease risk by quantifying parasitism rates and environmental levels of two common pathogens in different populations of each butterfly species that vary in their use of P. lanceolata. In the laboratory, genetic stock from these populations will be used to compare the immunological response to microbial pathogens and simulated parasitism among caterpillars feeding on P. lanceolata and ancestral host plant species. Researchers will experimentally investigate the interplay between diet, the sequestration of plant chemicals, and the bacteria residing in the insect gut by measuring the immune response when these factors have been manipulated. Finally, they will test whether larval infection history affects which plants are chosen by ovipositing females, or whether shifts to P. lanceolata reflect selection on innate host preference.