Quantitative Genetic Models for the Coevolution of Character Displacement

Abstract

The evolution of character displacement in competition communities was simulated with two quantitative genetic models. The first model is identical to that of Slatkin (1980) but we extend his analysis. The second model allows for the evolution of all niche attributes that affect interspecific competition along a resource axis. These are: the mean position of each species along the axis, the variation in position between phenotypes within each species, and the width of resources used by each phenotype. In addition, explicit dynamics for the resources are included in the model. This model predicts that character displacement can occur in coevolutionary communities. It also predicts that the relative niche separations between species (d/w ratios; d = distance between peaks of two species' niches on the resource (niche) axis, w = total niche width of a species) can be quite large, that the d/w values should decrease as species number increases, that at the evolutionary equilibrium, the within—individual component of the niche width will be much larger than the between—individual component, and that niche separation should be substantially smaller than character separation. These predictions are all in agreement with field observations surveyed from the literature.