DISSERTATION RESEARCH: Understanding how shifts from migratory to sedentary behavior influence host-pathogen dynamics

每年，数十亿只动物长途迁徙以追踪季节性资源。在某些情况下，这些迁徙通过降低传染病水平来促进健康的人口。如果在艰苦的旅途中将受感染的动物从种群中剔除，或者如果迁徙允许动物在一年中的部分时间逃离受污染的栖息地，就会发生这种情况。近几十年来，一些动物停止了迁徙，转而形成了常年繁殖的久坐种群，从而增加了有害病原体侵占种群的机会。例如，北美东部的所有帝王蝶曾经在每年秋天迁徙到墨西哥，但现在一些帝王蝶全年都留在美国南部，在那里它们以外来物种马利筋为食繁殖。这些久坐(非迁徙)的帝王面临着更大的感染风险，因为它们身上寄生了一种微小的寄生虫。该项目调查了这些久坐不动的君主是否会成为迁徙君主的感染源，或者导致更多的迁徙君主放弃迁徙，从而对迁徙君主构成风险。这项研究很重要，因为动物迁徙的变化可以改变野生动物的传染病水平，并可能影响病原体在野生动物和人类之间的传播。随着全球不同物种在迁徙过程中经历戏剧性的变化，了解这些变化的生态后果对野生动物和人类健康将是有价值的。该项目将促使公众帮助调查这一问题。自2006年以来，北美各地的数百名志愿者通过公民科学项目帝王健康对帝王进行了寄生虫感染采样。在这笔赠款的支持下，君主健康将招募新的志愿者进行捕获-标记-重新捕获调查，并将制作在线视频，突出公民科学家如何增强生态知识。最后，该项目有可能通过阐明种植外来乳草对帝王的影响来为帝王的保护做出贡献。具体地说，这项研究有两个目标：(1)确定久坐的帝王种群是否以某种方式导致迁徙的个体--特别是受感染的个体--停止迁徙，以及(2)确定久坐的种群是否作为迁徙种群的感染源。早期的研究表明，美国南部久坐不动的君主种群遭受着极高的原虫感染流行率。为了实现第一个目标，将在秋季迁徙期间在美国南部收集野生帝王，并进行化学分析，以区分迁徙和久居的个体。这些数据将被用来测试感染病毒的移民是否比健康的移民更有可能停止移民。为了实现第二个目标，将在春季对帝王进行实地采样，以区分久居的帝王和从墨西哥越冬地重新殖民美国的迁徙帝王，并量化这些群体之间的空间重叠程度。将监测这些地点幼年帝王的感染情况，以评估久坐不动的个体将病原体传播给迁徙个体的可能性。

Each year, billions of animals migrate long distances to track seasonal resources. In some cases, these migrations promote healthy populations by reducing levels of infectious disease. This occurs if infected animals are weeded out of the population during strenuous journeys or if migration allows animals to escape contaminated habitats for part of the year. In recent decades, some animals have stopped migrating, instead forming sedentary populations that breed year-round and leading to greater opportunities for harmful pathogens to take hold of populations. For example, all monarch butterflies in eastern North America once migrated to Mexico every fall, but some monarchs now remain year-round in the southern U.S., where they breed on exotic species of milkweed. These sedentary (non-migratory) monarchs face greater infection risk from a tiny parasite. This project examines whether these sedentary monarchs pose risks for migratory monarchs by acting as sources of infection or by causing more of them to abandon migration. This research is important because changes in animal migration can alter infectious disease levels in wildlife and may influence the transmission of pathogens between wildlife and humans. As diverse species around the globe undergo dramatic changes in migrations, understanding the ecological consequences of these changes will be valuable for wildlife and human health. This project will engage the public to help investigate this problem. Since 2006, hundreds of volunteers across North America have sampled monarchs for parasite infection through the citizen science program Monarch Health. With the support of this grant, Monarch Health will recruit new volunteers to conduct capture-mark-recapture surveys and will produce an online video to highlight how citizen scientists enhance ecological knowledge. Finally, this project has the potential to contribute to monarch conservation by elucidating how the planting of exotic milkweeds affects monarchs.Specifically, this research has two goals: (1) To determine whether sedentary populations of monarchs somehow cause migrating individuals -- particularly infected ones -- to stop migrating, and (2) to determine whether sedentary populations act as sources of infection for migratory populations. Earlier work showed that sedentary monarch populations in the southern U.S. suffer extremely high prevalence of protozoan infection. To accomplish the first goal, wild monarchs will be collected in the southern U.S. during fall migration and chemically analyzed to distinguish migratory from sedentary individuals. These data will be used to test whether infected migrants are more likely than healthy migrants to stop migrating. To accomplish the second goal, field sampling of monarchs will be done in the spring to distinguish sedentary monarchs from migratory monarchs re-colonizing the U.S. from their Mexican wintering grounds, and to quantify the extent of spatial overlap between these groups. Infections in larval monarchs at these same sites will be monitored to evaluate the potential for sedentary individuals to transmit pathogens to migratory individuals.