Niche Diversification and Coexistence of Insect Herbivores along the Food Quality Axis: Do Grasshoppers Ride the Rails?

Kansas State University, Manhattan KS

Investigators

Abstract

Based on new advances in functional nutritional ecology, this study addresses the central question: How important is food quality and availability for determining the number, composition and relative abundances of coexisting insect herbivore species? Primary nutritional quality (protein and carbohydrate levels) important to insect herbivore performance varies greatly in naturally occurring food plants, and species responses to variable food availability differ. Using controlled feeding studies, exact predictions about nutritional conditions that favor some species over others will be devised to predict coexistence and relative abundances of species. Research focuses on grasshoppers, which are abundant, diverse, functionally significant, and economically important insect herbivores found in most grassland. Nutritional intake targets supporting optimal performance ("balanced diets"), performance on suboptimal diets, and capacities of common grasshopper species to regulate nutritional intake to achieve balanced diets will be determined for food that varies in the ratio of protein:carbohydrate. Because leaf quality of naturally occurring food plants is not typically optimal to grasshoppers, the resulting analytical framework will predict how grasshoppers can respond to changing environments with suboptimal food - the typical situation. The ability of nutrition-based theory to predict patterns of species abundance and coexistence in grasshopper communities will be tested under naturally varying conditions.