"Ecological stoichiometry of North American grassland grasshoppers (Acrididae) along a latitudinal gradient"
Insect herbivores in grassland ecosystems encounter widely varying food quality embedded in a variable mosaic of primary production, plant species composition and nutrient dynamics. The PI's asked: how similar or how different are the underlying processes mediating these interactions in southern arid grassland compared to northern mixed-grass prairie? Do patterns associated with larger scales provide insight that cannot be obtained by studying a single or nearby grasslands? As dominant and diverse aboveground herbivores, grasshoppers are an excellent model insect herbivore to evaluate these processes for a wide array of native North American grasslands. The PI will examine constraints on grasshopper secondary production resulting from limiting nutrients across twelve sites ranging from arid grasslands in Texas to New Mexico, through a highly dynamic mid-continent set of sites comprising tallgrass, shortgrass and mixed grass prairies in Oklahoma, Kansas, Colorado and Nebraska until northern mixed grass systems in South Dakota and Canada are encountered. Four LTER sites will be included in this transect (Jornada, Sevilleta, Shortgrass Steppe and Konza Prairie).
Ecological stoichiometry provides the primary conceptual framework for addressing these key issues, employing the principle of mass balance to account for the regulation of limiting elements in their transfer between trophic levels. This research will examine stoichiometric elemental ratios (C:N:P) as a constraint on secondary production in grasshoppers. A series of predictions will be tested using C:N:P ratios of common grasshopper species, ingested food and grass from each of twelve sites. Sites that manipulate food quality with large experiments (fire, grazing and/or nutrient additions) provide an opportunity to better identify causal relationships.
