SEED DISPERSAL AND PATCH DYNAMICS IN TROPICAL RAIN-FORESTS - A DEMOGRAPHIC APPROACH

In this paper we propose that an evaluation of the ecological and evolutionary consequences of seed dispersal requires the recognition of patches where seeds have different probabilities to reach the seedling stage as well as the spatial and temporal dynamics of such patches. To analyze the relative importance of seed sources on the regeneration of trees growing in patchy environments, we use metapopulation models that combine matrix demographic models with Markovian models that simulate patch dynamics. The models are applied to the cases of two tree species with contrasting life-histories at Los Tuxtlas tropical rain forest, Mexico. For pioneer tree species, we show that the relative contribution of propagules from the seed rain and seed bank depends on the temporal regime of natural disturbance and the mortality rates of soil seeds. For shade-tolerant trees, results suggest that dispersal may increase seedling recruitment when seed movement occurs from patches where mother plants have higher fecundity and/or seeds have higher pre-dispersal survival to patches where soil-seeds and/or seedlings have higher survival. The metapopulation models also show that inferences about critical stages in the evolution of species life-histories contrast between a static and dynamic patchy scenario.