Modeling plant competition along an environmental gradient

The effect of an environmental gradient on inter-specific plant competitive interactions is modeled in a simple empirical model with biologically interpretable parameters. The model allows testing of hypotheses on the effect of the gradient on plant competitive interactions, as well as making ecological predictions from simple competition experiments using standard statistical procedures. The model, which is general and can be applied to different abiotic and biotic environmental gradients, is applied to a specific case of two competing Arabidopsis thaliana genotypes along a gradient of the general fungal pathogen Peronospora parasitica. One of the A. thaliana genotype is susceptible to the fungal pathogen P. parasitica and the other genotype is resistant. The Bayesian posterior distribution of the probability that the resistant genotype outcompetes the susceptible genotype is calculated as a function of the pathogen level. The design of the studied A. thaliana competition experiments is the minimum required experimental design needed to apply the model.