Factors affecting, and importance of, host species range in parasitic organisms: tests of hypotheses for causes and consequences.

野生动物和人类的寄生虫和病原体，从病毒和细菌到体内寄生蠕虫，每天都出现在世界各地的新闻头条中。即使是寻求可靠信息的媒体也承认，预测这种寄生虫和病原体对宿主个体和宿主种群（其中许多在环境或经济上具有重要意义）的影响是极其困难的。然而，我们对这些问题物种如何充当敌人的理解，对野生动物的管理、家养物种的生产和人类健康的保护具有重要意义。在许多情况下，我们认为寄生虫会比宿主占上风，因为它们之间的对抗性相互作用具有重要的不对称性。不对称性的出现是因为种群中并非所有的宿主个体都被给定的寄生虫物种的个体寄生。相比之下，所有寄生虫都必须找到并利用宿主才能成功。同样在许多寄生虫-宿主关系中，寄生虫的进化速度，基于世代时间和后代数量，比它们的宿主快得多。其他不对称性可能存在，例如宿主或寄生虫是否具有更高的传播率（这将新的遗传变异带入种群）。一个很大程度上未被探索的因素，可能与上述不对称性一样重要，是寄生虫物种利用一个以上宿主物种的程度。我们目前对为什么一些寄生虫物种是通才而另一些是专家知之甚少。我的发现补助金研究，与学生和合作者在未来5年，将集中在影响寄生生物的宿主物种范围的因素，使用模式生物。我们将测试广泛的宿主物种使用的原因和后果的假设。我们将部署观察，理论和实验方法，以确定哪些因素有利于开发特定的宿主物种，并预测对这些物种的影响。我们将利用这种理解来发展一个一般的理论，寄生虫物种和它们的少数到许多宿主物种之间的拮抗作用。

Parasites and pathogens of wildlife and humans, from viruses and bacteria to endoparasitic worms, are in news headlines around the world every day. What is acknowledged, even by the media seeking sound bytes, is that it is extremely difficult to predict the impact of such parasites and pathogens on host individuals and host populations (many of which are environmentally or economically important). Yet, our understanding of how these problem species act as enemies has strong implications for management of wildlife, production of domestic species, and protection of human health. In many instances, we expect parasites to have the upper hand over their hosts because of important asymmetries in their antagonistic interactions. Asymmetries arise because not all host individuals within a population are parasitized by individuals of a given parasite species. In comparison, all parasites must find and exploit a host(s) to be successful. Also in many parasite-host associations, the evolutionary rates of parasites, based on generation times and numbers of offspring, is much faster than that of their hosts. Other asymmetries likely exist such as whether it is the hosts or the parasites that have higher dispersal rates (which brings novel genetic variation into populations). One largely unexplored factor, likely as important as the asymmetries above, is the extent to which parasite species exploit more than one host species. We currently have little understanding of why some parasite species are generalists and others specialists. My Discovery Grant research, with students and collaborators over the next 5 years, will focus on factors affecting host species range in parasitic organisms, using model organisms. We will test hypotheses for causes and consequences of broad host species use. We will deploy observational, theoretical, and experimental approaches to ascertain which factors favor exploitation of particular host species and to predict impacts on those species. We will use such understanding to develop a general theory of antagonistic interactions between parasites species and their few to many host species.