Effects of grasshoppers on prairies: herbivore composition matters more than richness in three grassland ecosystems

1. Understanding how biodiversity affects ecosystem processes is a key question in ecology. Previous research has found that increasing plant diversity often enhances many ecosystem processes, but less is known about the role of consumer diversity to ecosystem processes, especially in terrestrial ecosystems. Furthermore, we do not know how general biodiversity responses are among ecosystem types. 2. We examined the role of insect herbivore (Orthoptera) diversity on plant production using parallel field experiments in three grassland ecosystems (mixed grass prairie, tallgrass prairie, and coastal tallgrass prairie) to determine if the effects of grasshopper diversity were consistent among sites. 3. Using mesocosms, we manipulated Orthopteran species richness (0, 1, 2, 3, or 4 species), functional richness (number of functional feeding groups present; 0, 1, or 2 functional groups), and functional composition (composition of functional groups present; mixed feeders only, grass feeders on...