PARENT SESSION
Poster Session #52: Evolutionary Ecology.
Thursday, August 8. Presentation from 8:00 AM to 9:30 AM. Exhibit Hall B & C, TCC

The role of resource availability in allocation between growth and storage in the grasshopper, Schistocerca americana.

Hahn, Daniel^*,1, ¹ The University of Arizona, Tucson, Arizona

ABSTRACT- Many organisms have been shown to change resource allocation strategies in response to resource availability. This flexibility 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 growth or storage for future use. It is unknown if allocation strategies between growth and nutrient storage at the larval-adult moult in insects are fixed or flexible. This work determines if the grasshopper, Schistocerca americana, has resource-mediated flexibility 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. The most nutrient poor diet contained 14% carbohydrates + proteins in a 1:1 ratio, and the most nutrient rich diet contained 84% 1:1 carbohydrates + proteins. Adult body size showed a positive quadratic relationship with nutrient content, and growth rate showed a negative quadratic relationship with nutrient content. 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 both more lipid and protein than animals on very nutrient rich or nutrient poor diets. However, there was no significant difference in allocation to nutrient storage across the diet treatments when body size was held constant. Thus, resource availability does not affect allocation patterns at the larval-adult moult in S. americana. Individuals maximize allocation to somatic growth, specifically body size, during development within the constraints imposed by resource availability.

KEY WORDS: resource allocation, nutrition, nutrient storage, growth