DISSERTATION RESEARCH: The interaction of environmental context and host attributes in driving parasitism

在生态系统迅速转变的时候，重要的是要澄清环境变化如何影响动物的疾病风险。由于气候变化，了解变暖对疾病的影响变得特别紧迫，但其净效应仍然存在争议和难以捉摸。这项研究将探讨水温如何改变水生宿主-寄生虫的相互作用，测试生长和发育的变化是否会与宿主及其寄生虫的生命周期不匹配，这是一种被认为在气候变化背景下很重要的机制，尽管对其进行直接测试并不常见。这项研究进一步确定了随着气候变化，疾病的哪些结果可能占主导地位，并将有助于预测温度对宿主-寄生虫相互作用的影响的框架。这项工作的更广泛的影响包括：1）教导K-12学生和公众关于宿主-寄生虫的相互作用，2）指导本科生，包括代表性不足的群体，进行独立研究并通过外展吸引公众，以及3）开发关于蜉蝣-寄生虫关系的互动儿童读物的情节。所有这些努力都集中在小动物上（例如，在测量了山溪（美国科罗拉多）的一系列环境变量后，有证据表明，气温升高会降低线虫感染蜉蝣的流行率。这一观察结果，结合先前的研究结果，即温暖的温度加快了蜉蝣宿主的发育速度，表明宿主和寄生虫生命周期的不匹配时间可能会减少温暖地区的寄生。由于温度不能很容易地从自然界中的其他环境变量中解脱出来，因此将使用受控的微观实验来验证以下假设：温暖的水会导致蜉蝣更快的发育，从而减少易感（早期）宿主与感染性寄生虫的重叠，并最终减少寄生虫感染。

At a time when ecosystems are rapidly transforming, it is important to clarify how environmental change affects disease risk for animals. Understanding the impact of warming on disease has gained special urgency due to climate change, but its net effect remains controversial and elusive. This study will explore how water temperature alters aquatic host-parasite interactions by testing whether shifts in growth and development could mismatch the life-cycles of a host and its parasite, a mechanism that is believed to be important in the climate change context, although direct tests of it are uncommon. This study constitutes a further step toward identifying which outcomes for disease are likely to dominate as the climate changes and will contribute to a framework for predicting effects of temperature on host-parasite interactions. The broader impacts of this work include 1) teaching K-12 students and the public about host-parasite interactions, 2) mentoring undergraduates, including under-represented groups, to do independent research and engage the public through outreach, and 3) developing the plot of an interactive children's book about the mayfly-parasite relationship. All of these efforts focus on small animals (e.g., parasites and invertebrates) to increase awareness of the full scope of biodiversity.After measuring a suite of environmental variables in mountain streams (Colorado, USA), evidence suggests that warmer temperatures decrease the prevalence of nematode worms infecting mayflies. That observation, combined with previous findings that warmer temperatures accelerate the developmental rate of mayfly hosts, suggests that the mismatched timing of host and parasite life-cycles could decrease parasitism in warmer areas. Because temperature cannot be readily disentangled from other environmental variables in nature, a controlled microcosm experiment will be used to test the hypothesis that warmer water causes faster development of mayflies, thereby decreasing the overlap of susceptible (early instar) hosts with infective parasites, and ultimately reducing parasite infections.