Insects that consume plant tissues have an inordinate impact on the health, survival and evolution of plant species, including all agricultural crops. In some cases, insect herbivores also alter the developmental and physiological programs of their host-plants, which cause the plants to produce more tissue for the benefit of the insect. The mechanisms by which insects cause these plant responses and the pathways by which insects evolved these remarkable abilities are largely unknown. This project will examine the evolution of these complex plant-herbivore interactions using the gall-wasp family, Cynipidae, as a model system. This family contains thousands of species that manipulate host-plants to create tumor-like structures, called galls, in which wasp larvae feed while being protected from predators and the outside environment. Galls vary tremendously in their architecture and location on the plant depending on the wasp species that initiated the gall. Researchers will generate genome-scale data to test how gall-wasps evolved the ability to make galls and how plant gall architecture has evolved over time. By examining the anatomy and physiology of these wasps, researchers will also shed light on how gall inducers are able to manipulate host-plants. The project will support the training of multiple early-career researchers, including members of underrepresented groups, and develop curricula that will improve insect biology education. Public outreach events will highlight the ecological and economic impact of insects in our society and will use the rich history of gall biology to engage diverse audiences. <br/><br/>The research team will resolve the evolutionary history of Cynipidae to determine whether gall induction evolved more than once in the family, establish whether viral or microbial symbionts are associated with galling, and determine how wasp species shifted among host-plant species over time. Researchers will reconstruct Cynipidae phylogeny using sequence data from 2,000 loci of ultra-conserved elements from more than 200 exemplar taxa, including every tribe and almost all genera. The evolution of gall induction strategies will be inferred from this tree using relevant meta-analyses, including ancestral states reconstruction, divergence time estimation, and comparative methods. Adult (venom) and larval (iliac, salivary) glands will be characterized for gross morphology, chemical composition, and transcriptomic profiles to uncover possible gall-inducing gene products, such as plant hormone mimics. Other outcomes of the research will include new diagnostic tools, expanded collections and genomic repositories, as well as a publicly-accessible database that will collate and synthesize historical gall-wasp research to accelerate description and discovery.<br/><br/>This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.