Resolving the tragedy of the commons: the feedback between intraspecific conflict and population density


Daniel J. Rankin, Laboratory of Evolutionary and Ecological Dynamics, Department of Biological and Environmental Science, PO Box 65 (Viikinkaari 1), FIN-00014 Helsinki, Finland.
Tel.: + 358 9 1915 7866; fax: +358 9 1915 7694;


Competition and conflict among individuals can favour exploitative strategies that undermine the common good. Theory suggests that this can lead to a tragedy of the commons and ultimately population extinction, a phenomenon known as evolutionary suicide. Here, I present a model of the evolutionary tragedy of the commons that explicitly considers the population dynamics where individuals invest in individually costly competitive traits. In the simplest form, this supports the notion that selection for high levels of conflict can cause evolutionary suicide. However, as competition comes with survival and fecundity costs, a feedback between the investment in competition and population density can act to reduce the level of conflict and prevent the population from going extinct. This suggests that the interaction between population ecology and the evolution of competition and conflict among individuals may be an important mechanism in resolving the level of competition and conflict among individuals.