MODELS FOR THE EFFECTS OF INDIVIDUAL SIZE AND SPATIAL SCALE ON COMPETITION BETWEEN SPECIES IN HETEROGENEOUS ENVIRONMENTS

A spatially explicit model for competition with dispersal in a heterog eneous environment is used to study the effects of individual size and the spatial scale of the environment on the competitive interactions between species. The model is a Lotka-Volterra competition system with diffusion and with spatial variation in some coefficients. The coeffi cients in the model are taken to reflect a situation where the larger competitor typically disperses farther in unit time than the smaller a nd reproduces less rapidly, but has an advantage in contests or other forms of interference competition. The environment is assumed to be cl osed, i.e., it is assumed that individuals do not leave through the bo undary. The environment is generally assumed to consist of a patch of favorable habitat surrounded by less favorable regions. The effects of spatial scale are studied by examining how the predictions of the mod el change as the size of the favorable patch is varied. The prediction s turn out to be in qualitative agreement with the results of some emp irical studies.