Allocation of energy to reproduction: Effects of competition and population structure

Abstract

A model is constructed to determine under what conditions a “competitor” strategist that allocates less energy to reproduction and more to competition with its neighbors is more successful than a “reproducer” strategist that allocates more energy to reproduction and less to competition. The success of these strategies is determined by their ability to invade a population of the opposite strategy. The competitor strategy is unlikely to invade and supplant the reproducer strategy in large populations. While population size has less impact on the ability of the reproducers to invade a population of competitors, increasing environmental variability greatly enhances the reproducers invasion success rate. The evolution of reproductive output is simulated for different population sizes. In small populations ( N = 20), the equilibrium reproductive output depends mainly on the level of environmental variability. For larger populations ( N = 60, 100), the equilibrium reproductive output depends more on the initial reproductive output. Reproductive output did not evolve in large populations as much as in small populations. The predictions of the model were compared to empirical patterns of resource allocation in plants and ants.