Characterizing the cost of oviposition in insects: a dynamic model

The development of a consensus model of insect oviposition has been impeded by an unresolved controversy regarding the importance of time costs versus egg costs in mediating the trade-off between current and future reproducti on. Here I develop a dynamic optimization model that places time and egg co sts in a common currency (opportunity costs expressed as decreased lifetime reproductive success) so that their relative magnitudes can be compared di rectly. The model incorporates stochasticity in host encounter and mortalit y risk as well as behavioral plasticity in response to changes in the age a nd egg load of the ovipositing female. The dynamic model's predictions are congruent with those of a simpler, static model: both time- and egg-mediate d costs make important contributions to the overall cost of oviposition. Mo dest quantitative differences between the costs predicted by the static ver sus dynamic models show that plasticity of oviposition behavior modulates t he opportunity costs incurred by reproducing females. The relative importan ce of egg-mediated costs increases substantially for oviposition events occ urring later in life. I propose that the long debate over how to represent the cost of oviposition should be resolved not by advocating the pre-eminen ce of one sort of cost above all others, but rather by building models that represent the complementary roles of different costs. In particular, both time and egg costs must be recognized to produce a general model of insect oviposition that incorporates a realistic representation of the cost of rep roduction.