Spatial variation in diurnal surface temperatures and the distribution and abundance of an alpine grasshopper.

We studied the influence of spatial differences in diurnal surface temperatures due to topography on an alpine grasshopper (Aeropedellus clavatus). Temperature measurements on east-and west-facing alpine dry meadow slopes on Niwot Ridge in Colorado demonstrated a significant difference in diurnal surface temperatures between the two slopes throughout the growing season. A. clavatus body temperature was found to be highly correlated with nearby shaded surface temperature, and individual grasshoppers enclosed on the two slopes had significantly higher relative growth rates on the warmer east slope. Temperature effects were manifest at the population level as well. A. clavatus was significantly more abundant on the east-facing than on the west-facing slope, despite similar vegetation in both areas. This study contributes to our understanding of the myriad of factors governing insect distribution and abundance by attempting to integrate the physiological and ecological, abiotic and biotic, influences on both individuals and populations.