Ecology and evolution of parasite-host relationships in a real ecosystem

寄生虫感染塑造了鱼类的进化和生态，但我们对寄生虫水平的变化如何迅速导致种群、群落和生态系统的变化知之甚少。我们提议的研究项目将通过与美国国家科学基金会(NSF)资助的500万美元研究计划合作来研究这些问题。这个NSF项目涉及对热带特立尼达岛上的整个溪流生态系统进行实验操作。特别是，孔雀鱼(一种小而多产的淡水鱼)将从捕食率和寄生率高的溪流引入以前没有孔雀鱼的溪流，其特点是捕食率和寄生率低。NSF团队在这次引进之后进行了非常详细的监测，这将使人们能够详细调查孔雀鱼进化变化的速度，以及对相互作用的物种和生态系统的任何后果。NSF项目完全专注于捕食的影响，而我们将增加寄生虫的维度。因此，我们的研究考察了保护鱼类种群免受其主要寄生虫影响的生态和进化后果。这是加拿大水产养殖业和濒危物种保护的常见战略，因此我们的结果将为这些活动的后果提供信息。例如，寄生率的减少可能会导致对寄生虫的抵抗力迅速丧失，从而在人群再次接触寄生虫时产生负面后果。与加拿大鱼类的潜在相关性特别可能是因为正在研究的特定体外寄生虫(Gyrodactylus)是加拿大淡水和海水鱼类的一种极其重要的病原体。我们提出的项目是新颖的，因为没有研究检验在其他自然生态系统中可控和重复的寄生实验操作的后果。这是及时的，因为NSF的实验将于今年春天开始，我们需要尽快让我们的采样团队到位。

Parasite infections shape the evolution and ecology of fishes, but we have little understanding of how rapidly changes in parasite levels lead to changes in populations, communities, and ecosystems. Our proposed research project will investigate these questions through collaboration with a 5 million dollar research initiative funded by the National Science Foundation (NSF) of the United States. This NSF project involves experimental manipulations of whole stream ecosystems on the tropical island of Trinidad. In particular, guppies (a small and prolific freshwater fish) will be introduced from streams characterized by high predation and parasitism into formerly guppy-free streams characterized by low predation and parasitism. Very detailed monitoring by the NSF team following this introduction will enable a detailed investigation of the speed of evolutionary change in the guppies and any consequences for interacting species and for the ecosystem. The NSF project focuses entirely on the effects of predation, whereas we will add the parasite dimension. Our study thus examines the ecological and evolutionary consequences of shielding a fish population from one of its major parasites. This is a common strategy in aquaculture and in the conservation of endangered species in Canada, and our results will therefore inform the consequences of these activities. For example, a reduction in parasitism may lead to a rapid loss of resistance to parasites, thus having negative consequences when populations are re-exposed to parasites. The potential relevance to Canadian fishes is particularly likely because the specific ectoparasite under study (Gyrodactylus) is an extremely important pathogen of freshwater and marine fishes in Canada. Our proposed project is novel because no studies have examined the consequences of controlled and replicated experimental manipulations of parasitism in otherwise natural ecosystems. It is timely because the NSF experiments commence this spring and we need to have our sampling team in place as soon as possible.