Meeting Abstract

P1.75A  Monday, Jan. 4  Grasshopper developmental plasticity in heavily-grazed Asian Steppe pastures CEASE, Arianne*; ELSER, James; HAO, Shuguang; KANG, Le; HARRISON, Jon; Arizona State University; Arizona State University; Chinese Academy of Sciences, Institute of Zoology; Chinese Academy of Sciences, Institute of Zoology; Arizona State University acease@asu.edu

Higher population density and reduced food quality promote formation of phenotypes with improved migratory capacity in many insects. We tested the effects of density and an N-fertilized plant diet on migratory polyphenism in Oedaleus asiaticus, a dominant pest across the Asian Steppe. This grasshopper has populations comprised of green and brown individuals. Anecdotally, it forms long-distance migrating swarms comprised primarily of brown individuals. Oedaleus population density and percent brown increased with grazing intensity. Oedaleus in heavily grazed pastures were warmer than species in ungrazed pastures. Percent brown increased with higher densities and decreased with N-fertilization. N-fertilization also decreased size and viability, suggesting that it decreased food quality. Brown hoppers had an increased metabolic rate (controlling for body size), were heavier due to increased hind leg and thorax mass, but had decreased jump performance relative to green forms. Neither form flew for long durations in a variety of flight trials, suggesting that neither form is prone to flight. Green-brown forms in O. asiaticus differ in many aspects of morphology and physiology and plastic changes in color respond similarly to population density and food quality as in other insects. However, color does not appear to be related to migratory capacity. This research was partially supported by a GPSA award from ASU, and ARCS award, and a Sigma Xi to AC and NSF DEB-0925017 to JE.