生物的适应性进化是当前生命科学的研究热点之一。病原生物（细菌、病毒、寄生虫等）给其动物宿主的免疫系统施加了很强的选择压力，促使与宿主免疫功能相关的基因产生适应性的遗传变异。因此，阐明动物免疫系统进化的分子机理具有重要的理论价值。作为多种病原生物的天然宿主和传播者，鸭科鸟类是研究动物免疫系统适应性进化的重要类群之一。本项目拟采用功能基因测序的方法，对Toll样受体基因家族在多种鸭科鸟类间和绿头鸭（Anas platyrhynchos）不同地理种群间的分子进化模式进行研究。Toll样受体是脊椎动物先天性免疫系统必要的元件，可以识别病原生物，从而激发宿主的免疫应答过程。但对野生鸟类Toll样受体基因进化模式的研究还较少。本项目旨在综合性地揭示鸭科鸟类Toll样受体基因在不同时空尺度下的进化模式。相关研究成果可丰富我们对鸟类免疫系统适应性进化的认识，并为阐明宿主与病原生物协同进化提供重要启示。

To investigate adaptive evolution of organisms is one of the most important issues and hotspots in current life sciences. Continuously evolving pathogens and parasites, usually leading emerging infectious diseases, pose strong selective forces on immune systems of their animals hosts. These consequently drive adaptive genetic variation at functionally important genes involved in the development of immune defense. Therefore patterns of pathogen-mediated selection acting on immune-defense genes in animals have been the focus of considerable interests for evolutionary biologists. Being natural reservoirs and probably potential vector species of several avian-borne diseases，long-distance migratory Anatidae birds, i.e. geese, swans and ducks, are one of important groups to study adaptive evolution of animal immune systems. To shed lights on the inter and intra specific evolution patterns of avian immune systems, evolutionary analyses will be carried out to investigate patterns of selection on Toll-like receptors multi-gene family, a branch of important genes involved in the resistance or susceptibility to infectious diseases. Toll-like receptors are characterized by trans-membrane structures that are functional in pathogen recognition. As a consequence, they initiate intracellular signaling cascade, which is essential for the activation of immune defense. However, the molecular evolution of Toll-like receptor genes in wild birds remains largely unknown. Hence, this project is to study genetic variability and characterize selection patterns of Toll-like receptor genes across several Anatidae species and conspecific populations of Mallard（Anas platyrhynchos）using a candidate-gene sequencing approach. This project is aim to gain comprehensive perspectives of evolutionary patterns of Toll-like receptor genes in Anatidae birds on a comprehensive tempo－spatial scales. Associated findings of this project will provide a base towards deeper understandings of the molecular basis of immune system evolution in wild birds, as well as important implications for host-pathogen coevolution.