Meeting Abstract

P1.152  Sunday, Jan. 4  High density and high nitrogen: A dual stressor for grasshoppers? CEASE, Arianne*; HAO, Shuguang; ELSER, James; KANG, Le; HARRISON, Jon; Arizona State University; Chinese Academy of Sciences; Arizona State University; Chinese Academy of Sciences; Arizona State University acease@asu.edu

Insects respond to high density in a variety of ways that, if exposed during larval development, can culminate in drastic changes in physiology and morphology. Some of these changes can be beneficial in aiding dispersal from a crowded habitat. For grasshoppers and other insect herbivores that tend to be nitrogen (N) limited, plant quality also affects these characters. High dietary N is correlated with increased survivorship, growth, and fecundity, while low dietary N is deleterious and can induce dispersal. Despite the intrinsic relationship between population density and dietary N, limited studies offer insight as to how the interaction of these two factors impact insect development. To gain a better understanding, we tested this in a dominant grasshopper species in Chinas Xilin River basin region, Odaleus asiaticus. Grasshoppers were assigned to 1 of 4 treatment groups (high or low density and N fertilized or unfertilized grass). There was a significant interaction effect between diet and density. Grasshoppers reared in high density and fed high N diets had a significantly lower growth rate, increased development time, decreased adult mass, and increased metabolic rate (MR) as compared with the other three treatment groups. Increased MR leads to increased energy expenditure and could explain decreased adult mass. It is also an indicative dispersal characteristic in this family. These results suggest that insects reared in high density are more sensitive to changes in dietary N, perhaps these effects are strictly deleterious due to a compound of stressors, or perhaps the interaction induces development of dispersal characters. This research was partially supported by NSF EAPSI fellowship and Sigma Xi GIAR to AJC.