CROWLEY, M.C.*; HATLE, J.D.; ANDREWS, A.L.; JULIANO, S.A.: Inter-population differences in reproductive tactics in lubber grasshoppers

For many organisms, a trade-off exists between reproductive timing (e.g. age at oviposition) and mass of reproductive output (e.g. number of eggs). Within a species, populations could be predicted to exhibit timing vs. output mass trade-offs that are adapted to their local environment. To test this hypothesis, we examined three populations of the clutch-laying grasshopper Romalea microptera. We predicted that grasshoppers from locations with relatively long growing seasons would have greater temporal reproductive plasticity and less plasticity in egg number. In contrast, grasshoppers from locations with relatively short growing seasons would have greater plasticity in egg number and less temporal plasticity. We used Florida (FL), Louisiana (LA), and Georgia (GA) hoppers as our long, intermediate, and short season populations, respectively. We reared three subsets of each population of grasshoppers with high, medium and low amounts of food available. For egg number, within each population, high-fed hoppers laid more eggs than low-fed hoppers. There were no significant differences in egg number among populations within a treatment. For time to oviposition, within each population, high-fed hoppers laid sooner than low-fed hoppers. In contrast to egg number, there were significant differences among populations within a treatment for age at oviposition. Both FL and LA medium-fed hoppers laid significantly later than GA medium-fed hoppers. There were no other significant differences among populations within a treatment. These data partly support our prediction that, in the trade-off between reproductive timing and mass output, long season hoppers will adjust reproductive timing and shorter season hoppers will adjust reproductive mass output.