The effects of variation in host plant availability and population densities on reproductive allocation in grasshoppers have received relatively little attention. The effect of increased host plant availability and population density on survival and reproductive allocation were examined in a widely distributed grasshopper, Ageneotettix deorum (Scudder). The experimental treatments consisted of ambient-level and fertilized vegetation with two A. deorum density treatments in a 2 × 2 factorial design. Both food plant availability and population density played important roles in the observed life history variation. Although the rate of egg pod production was not density-dependent, density-dependence was evident in the number of eggs per pod. Average survival did not respond to food plant availability, but reproduction was limited by host plant availability in the ambient-level treatment. Food limited A. deorum with ambient-level resources produced egg pods more slowly and with fewer eggs per pod. The rate of egg pod production averaged 64% higher with fertilized vegetation than with ambient vegetation. The availability of higher protein host plants may have been the primary limiting factor for egg production. The effects of food availability and grasshopper density acted in an additive manner on reproductive allocation. As a result, the per capita availability of nutrients was likely the limiting factor for reproduction in both resource and density treatments. Variation in host plant availability had a much larger effect on recruitment and population dynamics than would be predicted based on survivorship alone.
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Vol. 79 • No. 2