The Effect of Standard Metabolic Rate on Egg Production in the Acridid Grasshopper,Xanthippus corallipes

Abstract

SYNOPSIS. Models of energy budgets often allocate energy between the broad categories of maintenance, growth, and reproduction. An important component of maintenance costs is standard metabolic rate, which is partially determined by body temperature. The relationship between thermoregulation, standard metabolism, and egg production was investigated in adult females of the acridid grasshopper Xanthippus corallipes from six populations along an elevation gradient. Individuals thermoregulate and maintain stable afternoon body temperatures which correlate negatively with elevation. Standard metabolic rates were calculated at each population's afternoon body temperature. These rates were then used to investigate the effect of variation in standard metabolic rate on egg production. Because of the pervasive effect of mass on standard metabolic rate and egg number, the variables were log-transformed. The effect of mass was removed by regression analyses, and residuals were calculated. An analysis of the residuals revealed that intermediate values of field standard metabolic rate correlate with high egg production, suggesting stabilizing selection on standard metabolic rate.