Department of Zoology,University of Oxford,Mansfield Road, Oxford, OX1 3SZ,UK.
Parasitology. 2019 Jun;146(7):897-902. doi: 10.1017/S0031182019000015. Epub 2019 Feb 19.
Why some parasites evolve and maintain extreme levels of virulence is a question that remains largely unanswered. A body of theory predicts that parasites that form long-lived spores able to persist in the environment evolve higher virulence, known as the sit and wait hypothesis. Such parasites can obliterate their local host population and wait in the environment for further hosts to arrive, reducing some of the costs of high virulence. On the other hand, some models predict the opposite to be true, that virulence and environmental persistence are both costly and traded off, the resource allocation hypothesis. I conducted a meta-analysis on published data on the relationship between environmental persistence and virulence collected to date. I first examined all data available to date and then conducted a smaller analysis focussing on just those studies testing the specific predictions of the sit and wait hypothesis. Empirical work supports both hypotheses; however, the direction of the effect is largely associated with parasite type. In both analyses, viruses tend to show evidence of resource allocation trade-offs, these traits are positively correlated in bacterial and fungal parasites.
为什么有些寄生虫会进化并保持极端的毒力水平，这个问题在很大程度上仍未得到解答。有大量理论预测，能够形成在环境中存活的长寿命孢子的寄生虫会进化出更高的毒力，这被称为“坐以待毙”假说。这种寄生虫可以消灭其当地的宿主种群，并在环境中等待其他宿主的到来，从而降低高毒力的一些成本。另一方面，一些模型预测相反的情况才是正确的，即毒力和环境持久性都是有代价的，这被称为资源分配假说。我对迄今为止发表的关于环境持久性和毒力之间关系的文献数据进行了荟萃分析。我首先检查了迄今为止所有可用的数据，然后进行了一项较小的分析，专门针对那些检验“坐以待毙”假说具体预测的研究。实证研究支持这两种假说；然而，效应的方向在很大程度上与寄生虫的类型有关。在这两种分析中，病毒往往表现出资源分配权衡的证据，而细菌和真菌寄生虫的这些特征呈正相关。
