The physiological ecology of Daphnia II : a dynamic model of growth and reproduction

In the preceding paper (McCauley et al. 1990) we developed a new model for the growth and fecundity of Daphnia based on a quantitative review of short-term physiological rates and energy allocation for D. pulex. In this paper, we formulate a fully dynamic version of this model and test its predictions against experimentally observed growth and fecundity schedules obtained independently under a variety of different experimental protocols. Preliminary testing falsifies two simplifying hypotheses made in our original development and we propose modifications of these hypotheses. With the aid of these modifications our model yields predictions that are in good agreement with a large body of data on the growth and fecundity schedules of individual D. pulex. Although our model contains 18 parameters, the values of the great majority are independently determined from short-term physiological measurements, leaving only two as freely adjustable @'fitting parameters.@' The target dataset, which contains four complete growth curves (@?80 observations) and 32 growth or fecundity characterizations, thus provides a stringent test of the model, and our success in matching our predictions to it provides strong evidence that measurements of short-term physiological rates can be used successfully as predictors of long-term growth and fecundity