US-UKEEIDCollab:Understanding the effects of spatial structure on evolution of virulence in the real world: honeybees and their destructive parasites

个人倾向于与亲近的人或家庭或社会群体中的人进行更多的互动。因此，在通过接触传播的疾病中，受感染者更有可能接触与他们互动更多的某些社会群体中或附近的其他人。因此，这种疾病在空间上通过人口传播。已经有许多计算机模型表明，这种空间传播可能对疾病动态产生重大影响，但我们的工作表明，这种空间结构可能对寄生虫的进化产生重要影响。特别是，如果它们倾向于在局部传播，则它们被选择用于较低的传播和毒性。但我们如何检验这种理论呢？一种方法是实验性的，我们人为地操纵传播范围，并检查对寄生虫进化的影响。我们以前已经开发了一种昆虫病毒系统，我们可以在其中操纵宿主如何在本地移动。我们最近使用这个系统的工作证实了这个理论的预测;在粘性更强的种群中，毒力更低。这是对该理论的一个很好的实验检验，但我们现在提出看看这个理论是否与一个重要的真实的世界疾病系统相关。我们建议研究蜜蜂不同饲养方法产生的结构对其寄生虫瓦螨毒力的作用。蜜蜂受到各种寄生虫的威胁，其中瓦螨是最重要的寄生虫之一。我们将在重复实验设计中操纵螨的传播。传播的范围将从最近的殖民地之间的局部到全球的巨大差异。通过这种操作，我们将看到局部传播是否确实允许毒性较低的螨持续存在。我们将开发适合蜜蜂系统的新理论，并研究不同的蜜蜂饲养方法对寄生虫毒力的影响。此外，我们将开发新的理论，如何在宿主种群内的易感性变化对寄生虫毒力的影响，并在建立的蜜蜂系统内测试理论的预测。总体目标是更好地了解毒力如何演变，以改善疾病管理，特别关注蜜蜂的主要疾病。

Individuals tend to interact more with individuals that are close to them or within their family or social groups. It follows therefore that in diseases that are spread by contact, infected individuals are more likely to contact other individuals that are close by or within certain social groups with whom they interact more. The disease therefore spreads spatially through the populations. There has been a number of computer models that show that this spatial spread can have a major effect on the disease dynamics, but our work has shown that this spatial structure can have important implications to the evolution of parasites. In particular if they tend to spread locally, they are selected for lower transmission and virulence. But how do we test this kind of theory? One way is experimentally where we artificially manipulate the range of transmission and examine the impact on the evolution of the parasite. We have previously developed an insect virus system in which we can manipulate how locally the hosts move. and our recent work using this system has confirmed the predictions of the theory; virulence was lower in the more viscose population. This is a good experimental test of the theory, but we now propose to see whether this theory is relevant in an important real world disease system. We propose to examine the role of structure created by different rearing practices in the honeybee on the virulence of their parasite, the varroa mite. Honey bees are under threat from a wide range of parasites of which the varroa mite is one of the most important. We will manipulate transmission of the mite in a replicated experimental design. The transmission will range from local between nearest colonies to global over large differences. With this manipulation we will see whether local transmission does indeed allow less virulent mites to persist. We will develop new theory that is tailored to the honey bee system and examines how different bee rearing practices are predicted to impact on the virulence of the parasites. In addition we will develop new theory on how variation in susceptibility within host populations impacts on parasite virulence and test the predictions of the theory within the established honey bee system. The overall aim is to gain a better understanding of how to virulence evolves in order to improve the management of disease with a particular focus on a major disease of honey bees.