Spatial moment equations for plant competition: Understanding spatial strategies and the advantages of short dispersal

A plant lineage can compete for resources in a spatially variable environme nt by colonizing new areas, exploiting resources in those areas quickly bef ore other plants arrive to compete with it, or tolerating competition once other plants do arrive. These specializations are ubiquitous in plant commu nities, but all three have never been derived from a spatial model of commu nity dynamics-instead, the possibility of rapid exploitation has been eithe r overlooked or confounded with colonization. We use moment equations, equa tions for the mean densities and spatial covariance of competing plant popu lations, to characterize these strategies in a fully spatial stochastic mod el. The moment equations predict endogenous spatial pattern formation and t he efficacy of spatial strategies under different conditions. The model sho ws that specializations for colonization, exploitation, and tolerance are a ll possible, and these are the only possible spatial strategies; among them , they partition all of the endogenous spatial structure in the environment . The model predicts two distinct short-dispersal specializations where par ents disperse their offspring locally, either to exploit empty patches quic kly or to fill patches to exclude competitors.