On evolutionarily stable life histories, optimization and the need to be specific about density dependence

Concentrating on monomorphic populations in demographic steady state, we give three different conditions under which the evolutionarily stable life-history strategy can be characterized as the life-history strategy at which a relatively simple function is maximal. Depending on the way density dependence acts, this function, or fitness measure, can be the life-time production of offspring, the population growth rate, or another quantity from a large range of possible optimization criteria. We illustrate this by examining the optimal age at maturity for a hypothetical organism. All of this demonstrates that, when studying the evolutionary aspects of life-history characteristics, one cannot escape the task of specifying how density dependence limits population growth.