HAHN, D.A.; The University of Arizona: Resource mediated plasticity in allocation between growth and storage in the grasshopper, Schistocerca americana.

Many organisms have been shown to change resource allocation strategies in response to resource availability. This plasticity allows organisms to maximize fitness in different environments by changing allocation patterns. Body size and nutrient reserves are essential life history correlates of fitness. In insects, body size is fixed at the larval-adult moult, at which point resources accumulated by the larvae are invested into either somatic growth or storage for future use. It was previously unknown whether allocation strategies between growth and nutrient storage at the larval-adult moult in insects are fixed or flexible. This work demonstrates that the grasshopper, Schistocerca americana, has resource-mediated plasticity in its allocation strategy to growth and nutrient storage at the larval-adult moult. Resources were manipulated by rearing nymphs on artificial diets differing in total nutrient content from very poor to very rich. Animals feeding on diets with intermediate nutrient levels grew the largest, and did so most rapidly. Animals fed diets containing intermediate nutrient levels, were larger and stored proportionally more lipid than animals on very nutrient rich or nutrient poor diets. Thus, allocation strategies to growth and storage are plastic in response to larval nutrient availability in S. americana. Individuals maximize allocation to somatic growth, specifically body size, when resource availability is low, and split investment between somatic growth and lipid storage when resource availability is high.