The Evolution of Virulence under Conditions of Frequent Multiple Infections

一个单一的寄主个体通常含有一种以上的寄生虫。多种寄生虫之间的相互作用可以影响毒力的进化轨迹（寄生虫引起的宿主适应性丧失），具有重要的生态和流行病学后果。我们目前对毒力进化的理解受到缺乏长期研究的严重限制，特别是那些涉及具有不同传播模式和开发策略的不同寄生虫物种的研究。短期实验室研究大多排除了宿主间的选择，而进化模型的预测基于宿主内和宿主间选择的结合，两者之间存在差距。本研究以水蚤及其微寄生虫为模型系统，探讨不同寄生虫多种感染对水蚤毒力进化的长期影响。与以前的工作相比，我们的实验方法将包括宿主之间的选择。此外，我们将研究不同情况下的毒力进化：当竞争寄生虫利用不同/相同的宿主组织时；具有不同/相同的传输方式；并且具有不同/相同的传播起点。重要的是，我们将把实验室实验的结果与自然种群的实地研究结果联系起来，因为理解寄生虫物种之间复杂的相互作用关键取决于所考虑的规模。这项拟议的研究是以色列和德国科学团队密切合作的结果，将进一步加深我们对形成毒性演变过程的理解。该项目还将促进对寄生虫传播到新地区的后果进行新的和精确的预测。这种入侵情况可能导致以前从未同时发生的寄生虫之间的共同感染。两位应用研究人员的匹配和他们互补的科学专业知识预示着一次成功的合作，其结果将对进化生态学领域做出重大贡献。

A single host individual often harbors more than one parasite species. The interactions between multiple parasite species can affect the evolutionary trajectory of virulence (the parasite-induced loss in host fitness), with important ecological and epidemiological consequences. Our current understanding of virulence evolution is seriously constrained by the lack of long-term studies, particularly those involving different parasite species with diverse modes of transmission and exploitation strategies. There is a gap between short-term laboratory studies, which mostly exclude between-host selection, and predictions from evolutionary models, which are based on a combination of within- and between-host selection. The goal of the proposed work is to investigate the long-term implications of multiple infections by different parasite species on the evolution of virulence, using Daphnia and their microparasites as a model system. In contrast to previous work, our experimental approaches will include between-host selection. Moreover, we will study virulence evolution under different scenarios: when competing parasites exploit different/the same host tissues; have different/the same transmission mode; and have different/the same onset of transmission. Importantly, we will relate the results of laboratory experiments to findings from field studies of natural populations, as understanding complex interactions among parasite species depends critically on the scale under consideration. The proposed research, a result of close collaboration between Israeli and German scientific teams, will further our understanding of the processes that shape the evolution of virulence. This project will also stimulate new and refined predictions regarding the consequences of the spread of parasites into new regions. Such invasion scenarios can result in co-infection between parasites that have never previously co-occurred. The match between the two applying researchers and their complementary scientific expertise promises a successful collaboration whose results will be a significant contribution to the field of evolutionary ecology.