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，弄清环境变化如何影响动物的疾病风险是很重要的。由于气候变化，了解气候变暖对疾病的影响变得特别紧迫，但其净影响仍然存在争议和难以捉摸。这项研究将通过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来探索水温如何改变水生宿主-寄生虫的相互作用，这一机制被认为在气候变化背景下是重要的，尽管直接测试它是不常见的。这项研究是朝着确定随着气候变化可能主导哪些疾病后果的进一步步骤，并将有助于建立一个框架来预测温度对宿主-寄生虫相互作用的影响。这项工作的更广泛影响包括1)向K-12学生和公众传授宿主-寄生虫相互作用的知识，2)指导本科生，包括代表不足的群体，进行独立研究，并通过外联让公众参与进来，以及3)开发一本关于蚂蚁-寄生虫关系的互动儿童书的情节。所有这些努力都集中在小动物(例如寄生虫和无脊椎动物)上，以提高人们对生物多样性的全面认识。在测量了一系列山区溪流(美国科罗拉多州)的环境变量后，证据表明，温度升高会降低感染蚂蚁的线虫的流行率。这一观察，再加上之前的研究结果，即温度升高会加速蚂蚁寄主的发育速度，表明寄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率。由于温度不能很容易地从自然界的其他环境变量中分离出来，因此将使用受控的微观世界实验来检验这样的假设，即更温暖的水会导致蚂蚁更快地发育，从而减少易感宿主(早期幼虫)与感染性寄生虫的重叠，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.