Group selection in density-regulated populations revisited

Recent theoretical studies have indicated that the evolution of cooperation can be severely constrained by the spatial scales over which density regul ation acts. If density regulation occurs on a local scale within a group, v ariation in productivity among groups is suppressed and the among-group com ponent of selection is eliminated. Here, I present the results from a simpl e model that shows that there is more scope for the evolution of cooperatio n under density regulation than previously thought. This statement, however , is conditioned upon the fact that the traits under selection are themselv es involved in the density-regulating process. Furthermore, the results als o suggest that traits directly involved in the density-regulating process, such as various competitive strategies or interference behaviours, are like ly candidates for evolution through group selection, since they are not con strained by the ecological population structure to the same degree as other traits are. Laboratory experiments on group selection may provide some sup port for this hypothesis, since many traits that have been shown to be invo lved in the response to group selection are either directly or indirectly r esponsible for determining the strength of intraspecific competition.