Egg size evolution and energetic constraints on population dynamics

We use population models that are based on dynamic energy budget models for individuals in order to study the evolution of offspring size and its rela tionship to the evolution of population dynamics. We show the existence of alternative evolutionarily stable strategies for offspring investment strat egy resulting from a trade off between offspring number and time-to-maturit y. The model predicts egg energy in Daphnia magna well, and suggests that t he observed egg energy in D. magna is the result of selection for minimal e gg investment constrained by minimum viable egg energy, combined with selec tion for a juvenile energy reserve. The selection for minimal egg size push es populations toward chaotic dynamics. However, the minimum viable egg siz e combined with low efficiency of conversion of energy to new biomass is su fficient to keep population dynamics out of chaos. (C) 2001 Academic Press.