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，从病毒和细菌到内生蠕虫，每天都会出现在世界各地的新闻头条。即使是寻求合理字节的媒体也承认，预测这种寄生虫和病原体对宿主个人和宿主种群(其中许多是环境或经济上重要的)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，对于野生动物的管理、家养物种的生产和保护人类健康具有重要的意义。 在许多情况下，我们预计寄生虫会在它们的宿主上占据上风，因为它们之间的拮抗作用存在重要的不对称性。不对称性的产生是因为不是一个种群中的所有寄主个体都被给定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(S)才能成功。同样，在许多寄生虫-宿主关系中，基于世代次数和后代数量的寄生虫的进化速度比它们的宿主快得多。其他不对称性可能存在，例如是宿主还是寄生虫具有较高的传播率(这将为种群带来新的遗传变异)。 一个很大程度上未被探索的因素，可能与上面的不对称性一样重要，那就是寄生虫物种利用不止一个宿主物种的程度。我们目前对为什么一些寄生虫物种是多面手，而另一些是专家，知之甚少。在接下来的5年里，我与学生和合作者一起进行的探索奖助金研究将利用模型生物，重点研究影响寄生生物寄主物种范围的因素。我们将检验广泛使用寄主物种的原因和后果的假设。我们将采用观察、理论和实验方法来确定哪些因素有利于开发特定的寄主物种，并预测对这些物种的影响。我们将利用这样的理解来发展一个关于寄生虫物种和它们的少数对多个宿主物种之间的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.