Intraspecific and interspecific variation in metabolic rate across an elevational gradient in Australian mountain grasshoppers

Abstract

Metabolic rate provides a fundamental linkage between individual energetics and population ecology. Exploring variation in metabolic rate and other traits across environmental gradients such as elevation provides insights into the selective pressures operating in different habitats. Moreover, this variation reveals evolutionary and ecological consequences of individual energetics. Metabolic rate is influenced by temperature and body mass of organisms. Numerous studies have suggested different mechanisms by which body mass and metabolic rate vary with elevational gradients. The metabolic cold adaptation hypothesis proposes that metabolic rate is higher for populations from colder climates. The temperature-size rule indicates that body size should increase with decreasing temperature. Yet, these generalised observations remain controversial. Therefore, we investigate the intraspecific variation in body mass and metabolic rate in Monistria concinna (Walker, 1871) and then use Kosciuscola cognatus Rehn, 1957 for interspecific comparison of metabolic rates. We found that M. concinna reverses the temperature-size rule and displays sexual dimorphism. Elevation and sex are significant determinants of body mass and metabolic rate in M. concinna. Our data suggest that M. concinna and K. cognatus do not show metabolic cold adaptation. Our data also support previous suggestions of an asymmetry in insect cold physiology between the northern and southern hemispheres.