Evoluationary Consequences of Density Dependence on Optimal Maturity in Animals with Indeterminate Growth

Abstract

We consider life history consequences of density dependence to age at maturity in populations of freshwater clams. We study in particular the trade-off between growth and reproduction. For the purposes of the analysis we developed an age-structured population dynamics model for animals with indeterminate growth. In modelling evolution, we apply the concept of evolutionarily stable strategies (ESS) and compare them to the traditional density independent optimization criteria, or fitness measures, r and R0. Population regulation by density substantially affects the optimal timing of maturity. Different types of density dependence may produce both quantitatively and qualitatively different predictions for ESS age at maturity. We conclude that the way in which density dependence works in populations is essential for analysing life history evolution and population dynamics. As a whole, density dependence should be considered as an important evolutionary force, affecting the key fitness components like death and birth rates either directly, or indirectly via changes in e.g. growth rate.