International DDEP: Grasshopper migration in the Asian steppe: investigating diet as a cue for polyphenism

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This Doctoral Dissertation Enhancement award will support field research on grasshopper migration in China by Ph.D. student Arianne Cease of Arizona State University. Several specific questions will be addressed in this research including: 1) Do migratory forms of grasshopper result from superior or inferior diet quality? 2) Can transitions between migratory and nonmigratory forms be triggered by changes in specific plant characteristics, such as nitrogen, carbon, phosphorus, or alkaloid content? 3) Does overgrazing stimulate formation of migratory forms by lowering plant nutritional quality? To address these questions, the density and diet of Oedaleus asiaticus will be manipulated in the lab and observed in the field, and morphological, physiological and behavioral responses of developing grasshoppers will be recorded. This award will promote a highly interdisciplinary collaboration by a group of NSF-funded ecologists and insect physiologists with grasshopper biologists and grassland botanists in China. Collaborative activities funded by this award will include research at the Beijing Institute of Life Sciences and the State Key Laboratory of Integrated Management of Insect & Rodent Pests involving multiple Chinese and US scientists. Finally, this research will provide critical data necessary to understand and potentially prevent disastrous locust swarms. During an outbreak year, swarming grasshoppers (locusts) can populate 11 million square miles of land worldwide, negatively affecting more than 60 countries and the livelihood of 1 out of every 10 people. Global climate change is predicted to increase precipitation variability and perhaps exacerbate locust outbreaks. While it is often hypothesized that dietary cues related to deteriorating environmental conditions might trigger locust swarms, the specific dietary cues that may cause this developmental plasticity are unknown. This research will investigate the question in China, using the grasshopper O. asiaticus, one of two economically important outbreak locusts in Asia. This research will also establish long-term international research ties and promote a globally engaged scientific workforce focused on an important agricultural problem.