Life history consequences of fixed costs of reproduction

The distinction between fixed and variable factors of production and their corresponding costs has: long played a fundamental role in economic theory. However, in analyses of life history evolution a distinction between fixed and variable costs of reproduction has not been made. In this paper. I dis cuss these concepts and analyze some effects of fixed costs of reproduction on reproductive decisions. While some fitness functions do not allow fixed costs of reproduction to affect optimal reproductive effort, others do. In creasing fixed costs reduces total fitness and increases the level of inves tment required to obtain a reproductive profit. Increased fixed costs may a lso narrow the parameter space of reproductive effort for positive profit. These results are discussed in the perspectives of age at maturity and the evolution of semelparity.