XVI International Botanical Congess

To understand the effects of particular plant-animal interaction on plant fitness requires a model that includes the appropriate pattern of variability across both space and time. Two approaches to model such variation are the megamatrix and the stochastic sequence. In both cases, each variant of the habitat is represented by a matrix of demographic transitions for that habitat and each variant of the outcome of an interaction is represented by its effect on a transition in a given habitat. In the first approach, dynamics are given by eigenvalue analysis of a matrix that includes all possible transitions among each stage-habitat combination. In the second approach, dynamics are simulated by drawing matrices sequentially according to probability rules. These two methods give different estimates of the effects of interactions, such as mutualists and enemies, on plant fitness.