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，从病毒和细菌到内寄生蠕虫，每天都是世界各地的新闻头条。即使是寻求声音字节的媒体也承认，预测这些寄生虫和病原体对宿主个体和宿主种群（其中许多对环境或经济具有重要意义）的影响是极其困难的。然而，我们对这些问题物种如何作为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，我们预期寄生物会比寄主占上风，因为它们的拮抗相互作用存在重要的不对称性。不对称的产生是因为并非一个种群中的所有宿主个体都被某一种寄生虫的个体所寄生。相比之下，所有寄生虫都必须找到并利用宿主才能成功。此外，在许多寄生物-寄主关系中，基于世代次数和后代数量，寄生物的进化速度要比寄主快得多。其他不对称也可能存在，比如是宿主还是寄生虫具有更高的传播率（这给种群带来了新的遗传变异）。一个很大程度上未被探索的因素，可能与上述不对称一样重要，是寄生虫物种利用多个宿主物种的程度。我们目前对为什么一些寄生虫是通才而另一些是专才知之甚少。我的发现基金研究，与学生和合作者在未来5年，将集中在影响寄生生物宿主物种范围的因素，使用模式生物。我们将测试关于广泛使用宿主物种的原因和后果的假设。我们将采用观察、理论和实验的方法来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。我们将利用这样的理解来发展寄生虫物种与其少数到许多宿主物种之间拮抗相互作用的一般理论。

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.