Genetic Tradeoffs in Resistance to Natural Enemies

理论上，寄主对寄生虫的抗性和寄主适应性性状之间的权衡在维持遗传变异中起着关键作用，从而决定了抗性的进化潜力。本研究将对寄主生活史和生态特征进行全面的权衡实证研究，并将利用果蝇-螨虫系统作为模型来解决几个关键假设。这些假设是，在没有寄生虫的情况下，在实验室中选择的对寄生螨更有抵抗力的菌株将遭受卵孵化成功率、争夺有限资源的能力、存活率和繁殖能力以及对其他天敌的防御能力的显著降低。这些敌人包括一种无脊椎动物捕食者和一种昆虫致病菌。另一个重点将是测试在已知宿主生物在自然界中所暴露的可变环境条件下是否存在抗性成本。在脊椎动物宿主-外寄生虫的相互作用中，以及昆虫猎物和捕食者之间的相互作用中，可以看到许多介导果蝇-寄生螨关联的因素。因此，所提出的工作结果应该为理解广泛的动物物种的抗性机制和进化提供重要的数据。所产生的数据还可望有助于确定选择适当的天敌，特别是天敌混合物的标准，以便有效地进行生物虫害防治。因此，这项研究应有助于减少对化学农药和除草剂使用的依赖，从而促进环境健康。我们对多物种关联及其生态复杂性的一般认识也应该得到提高。这项研究工作将有助于培养本科生和研究生，并应具有实用和社会价值，因为它有望帮助开发可持续生物防治的新方法。

In theory, tradeoffs between host resistance against parasites and host fitness traits play a key role in the maintenance of genetic variation and hence in determining the evolutionary potential of resistance. The proposed research encompasses a comprehensive empirical study of tradeoffs focusing on host life history and ecological traits, and will utilize a Drosophila-mite system as a model to address several key hypotheses. These hypotheses are that strains selected in the laboratory to be more resistant to parasitic mites will suffer, in the absence of the parasites, significant reductions in egg hatch success, ability to compete for limiting resources, survivorship and fecundity, and in defensive capabilities against other natural enemies. These enemies include an invertebrate predator and an insect-pathogenic bacterium. Another major emphasis will be to test for the presence of costs of resistance under variable environmental conditions to which the host organism is known to be exposed in nature. Many of the elements that mediate the Drosophila-parasitic mite association are seen in vertebrate host-ectoparasite interactions, and in associations between insect prey and their predators. Thus the results of the proposed work should provide data of importance toward understanding the mechanisms and evolution of resistance across a broad array of animal species. The data generated are also expected to help define criteria for choosing appropriate natural enemies, and especially mixtures of natural enemies, for effective biological pest control. The research should therefore help to reduce dependency on chemical pesticide and herbicide usage, and hence promote environmental health. Our general knowledge of multispecies associations and their ecological complexities should also be advanced. The research effort will contribute to the training of both undergraduate and graduate students, and it should be of practical and societal value as it is expected to help develop novel methods of sustainable biological control.