桔二叉蚜和桔蚜是亚热带重要经济作物害虫，两者虽为蚜属声蚜亚属的近缘物种，在中国南方有类似的地理分布，却有截然不同的寄主植物利用范围，这使得它们是研究作物害虫适应演化和种群分化机制的理想模型。在良好的前期研究基础上，本项目将开展大规模取样，获取包括蚜虫线粒体基因序列、微卫星数据和内共生菌基因序列等在内的分子数据，以及蚜虫形态测量数据，比较研究两种蚜虫的种群分化及寄主植物特化机制，重点检验两种蚜虫是否形成对应于不同寄主植物的种群分化、是否受地理因素影响形成特定的种群空间格局、以及两种蚜虫寄主植物利用格局是否受内共生菌的影响等科学问题。本项目的开展不但可以增进对蚜虫种群演化及为害机制的理解，也将为两种害虫的生态防控提供重要证据。

Aphis (Toxoptera) aurantii and A. (T.) citricidus are two aphid pests of many subtropical economic plants. Although they are close species of the same subgenus, and have similar distributions in southern China, they show distinctly different patterns of host-plant use. These biological characteristics suggest the two aphid species are good models to study population differentiation and adaptive evolution of herbivorous pest. Based on informative exploratory researches, this program aims to investigate population differentiation and host-plant specialization of the two species. By incorporating gene sequence and microsatellite data as well as morphometric measurements, we test whether population differentiation of the two species is influenced by host plants and geographical factors, and whether the patterns of host-plant use is determined by aphid endosymbionts. The outputs of this program should improve understanding of population evolution of aphid pests and provide scientific evidence for ecological pest management.