Evolution of Complex Life Cycles and Host Relationships in Pemphigine Aphids

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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.