Dissertation Research: Synergistic Effects of Predators and Trematode Parasites on Larval Amphibians

寄生虫和捕食者除了直接影响动物的生存和繁殖外，还可以以各种复杂的方式影响动物。例如，寄生虫可以通过影响宿主的行为或其他特征来改变宿主对捕食者的易感性。同样，通过视觉或化学线索(如气味)感觉到捕食者靠近的猎物可能会改变它们的行为，这可能会影响它们对寄生虫的敏感性。这种复杂的影响可能会对群落内的每个物种产生不同的影响，这可能会以牺牲其他物种为代价，使一些物种受益。因此，受捕食者和寄生虫共同影响的动物群落看起来可能与只受其中一种天敌影响的群落截然不同。该项目将评估棘口吸虫(一种吸虫寄生虫)和捕食者如何相互作用，影响池塘中的青蛙(蝌蚪)幼虫群落。首先，将测量不同种类的幼蛙在有和没有捕食者的情况下对棘口吸虫感染的敏感度。其次，我们将研究捕食者和寄生虫对一个简单的青蛙幼虫群落的交互作用。在人工池塘中的一项实验将证明寄生虫感染率在多大程度上取决于两栖动物群落的组成和捕食者的存在。结果还将揭示感染和捕食者线索的组合如何影响幼蛙之间对资源的竞争。最后，一项实地调查将建议这些影响如何在密歇根州东南部的天然池塘中发挥作用。因此，这项研究将为寄生虫和捕食者影响群落的复杂机制提供新的见解。从保护的角度来看，这一结果将是有价值的，因为在与人类影响相关的地区，如污染和城市化，棘口棘口的存在水平较高。由于捕食者对两栖动物群落有很大的影响，了解它们与这些池塘中的寄生虫的相互作用将特别重要。此外，两栖动物是一类特别令人关注的动物，因为许多种群在全球范围内正在下降，部分原因是疾病。这项研究将涉及与当地组织、本科生、K-12组织和土地所有者的合作，这将为公共宣传和教育提供一个极好的机会。

Both parasites and predators can affect animals in a variety of complex ways in addition to directly affecting survival and reproduction. For instance, parasites can change how susceptible their hosts are to predators by affecting host behavior or other traits. Similarly, prey that sense a predator is near through visual or chemical cues (e.g., smell) may change their behavior, which may affect their susceptibility to parasites. Such complex effects can impact each species within a community differently, which may benefit some species at the expense of others. As a result, an animal community affected by the combination of predators and parasites may look very different than a community affected by only one type of these natural enemies. This project will evaluate how echinostomes (a trematode parasite) and predators interact to affect larval frog (tadpole) communities in ponds. First, the susceptibility of different species of larval frogs to echinostome infection in the presence and absence of predators will be measured. Second, the interactive effects of predators and parasites on a simple community of larval frogs will be examined. An experiment in artificial ponds will demonstrate the extent to which parasite infection rates depend on the composition of the amphibian community and the presence of predators. The results will also reveal how the combination of infection and predator cues affects competition for resources among larval frogs. Finally, a field survey will suggest how these effects play out in natural ponds in Southeast Michigan. This research will thus provide new insights into complex mechanisms through which parasites and predators affect communities. The outcome will be valuable from a conservation perspective because echinostomes are present at higher levels in areas associated with human impacts, such as pollution and urbanization. Because predators have a strong impact on amphibian communities, their interactions with parasites in these ponds will be particularly important to understand. Additionally, amphibians are a class of special concern because many populations are in decline globally, in part due to disease. This research will involve collaboration with local organizations, undergraduate students, K-12 organizations, and landowners, which will provide an excellent opportunity for public outreach and education.