Grasshopper (Orthoptera: Acrididae) communities on an elevational gradient in southwestern Montana

We examined variation in acridid grasshopper community composition along a 1650 m elevational gradient in southwestern Montana. As elevation increased, the most abrupt change in community composition occurred in the foothills of two mountain ranges (1800-1950 m). Most of the species abundant on the lower elevation sites (1400-1500 m) in this and a previous survey were rare or absent at elevations of 1800-3050 m. Melanoplus oregonensis, which was relatively rare at the lower elevation sites, was the most abundant species at elevations >2000 m. A number of the species characteristic of our high elevation sites have also been identified as high elevation species in other areas of the Rocky Mountains of Colorado and Wyoming. Although grasshopper community composition, species richness, species diversity, and abundance were correlated with elevation, they were not correlated with plant species richness, plant species diversity, or total plant cover, which peaked at mid-elevations. Elevation, through its effect on temperature, may be important because grasshopper developmental rates and minimum developmental threshold temperatures vary among species.