Evolution of Complex Life Cycles and Host Relationships in Pemphigine Aphids

[807076 . 76]冯多伦蚜虫是一群以植物汁液为唯一食物来源的昆虫。由于这种摄食模式，蚜虫进化出了久坐不动的生活方式和简化的形态；其中一些是毁灭性的农业害虫。一些蚜虫群体还进化出复杂的生命周期，包括在几代无性系之间在不相关的植物宿主之间进行强制性的季节性迁徙。此外，这些群体的成员经常引起其宿主或胆囊的变形，结构从简单到复杂。该合作项目结合了Carol von Dohlen（分子系统学）和两位日本科学家Shigeyuki Aoki和Utako Kurosu（蚜虫分类学）的专业知识，应用分子系统发育方法重建具有复杂生命周期的蚜虫的进化史。基因扩增（聚合酶链反应），克隆和测序的方法将被用来获得几个基因的DNA序列约63种蚜虫。这些数据将用于重建最古老蚜虫亚科之间的进化关系，以及天疮亚科内分类群的关系。关于生命周期类型、寄主植物和瘿形式之间的历史过渡的具体假设将用当前重建进化树的方法进行测试。我们的研究将解决以下问题：在较老的蚜虫谱系中复杂生命周期的起源数量，这些周期是否可能由不同的机制起源，不同寄主植物分类群之间的转移是否很少或频繁，以及复杂瘿结构的起源是否导致物种多样性增加。这个项目将增加我们对昆虫和寄主植物之间进化相互作用的理解，昆虫类群的历史很难在形态学的基础上重建。此外，它将促进地理位置遥远、兴趣和技能长期互补的科学家之间的知识交流和沟通。

9807076 Von Dohlen Ahids comprise a group of insects that tap plant sap as a sole food source. As a consequence of this feeding mode, aphids have evolved sedentary life styles and simplified morphologies; several are devastating agricultural pests. Some groups of aphids also have evolved complicated life cycles that incorporate obligate, seasonal migrations between unrelated plant hosts over several clonal generations. In addition, members of these groups often induce deformations of their hosts, or galls, with simple to complex structure. This collaborative project joins the expertise of Carol von Dohlen (molecular systematics) and two Japanese scientists, Shigeyuki Aoki and Utako Kurosu (aphid taxonomy) in applying molecular phylogenetic methods to reconstruct the evolutionary history of aphids with complex life cycles. Methods of gene amplification (polymerase chain reaction), cloning, and sequencing will be employed to obtain DNA sequences of several genes for approximately 63 aphid species. These data will be used to reconstruct evolutionary relationships among the most ancient aphid subfamilies, as well as relationships of taxa within the subfamily Pemphiginae. Specific hypotheses concerning the historical transitions between life cycle types, host plants, and gall forms will be tested with current methods for reconstructing evolutionary trees. Our research will address questions concerning the number of origins of complex life cycles among older aphid lineages, whether such cycles may have originated by different mechanisms, whether shifts among different host-plant taxa have been few or frequent, and whether origins of complex gall structure have led to increased species diversity. This project will increase our understanding of the evolutionary interactions between insects and host plants for an insect group whose history has been difficult to reconstruct on the basis of morphology. In addition, it will promote intellectual exchange and communication between geographically remote scientists with long-standing, complementary interests and skills.