A theoretical examination of growth and mortality tradeoffs on population growth rate and size structure

A stage-structured discrete time model was used to examine how size-specific tradeoffs between biomass accumulation and predation risk are influenced by changes in reproductive mode in a theoretical population. The size class with the largest aggregate growth rate, the product of the biomass accumulation rate and probability of survival, was found to be an absorbing class such that any reproductive strategy combined with a specified tradeoff which yields a larger proportion of individuals of the dominant size class should be favored. This model suggests that the steepness of the selection gradient for this reproductive mode becomes increasingly shallow when populations exhibit frequent switching between size classes. This model also suggests that selection gradients may become steeper or shallower depending on changes in the nutrient or predation environment.