GROWTH IN MEDEOLA VIRGINIANA CLONES. II. STOCHASTIC SIMULATION OF VEGETATIVE SPREAD.

Abstract

Medeola virginiana, a forest understory herb, has been hypothesized to minimize competition among ramets by positioning ramets regularly in space (Bell, 1974). We have constructed a computer model that simulates vegetative spread in Medeola by incorporating the variation in growth form found in natural populations. This stochastic model, based on data in Cook (1988), includes variation in the number and type of daughter ramets, the distance between parent and daughter ramets, and the angle of divergence between the lines of growth of the parent and daughter rhizomes. Over a wide range of initial ramet densities, initial degrees of ramet dispersion, and intensities of ramet mortality, our simulations indicate that the growth pattern of M. virginiana leads to aggregated distributions of ramets with overlapping leaf canopies. The observed aggregation of ramets may result from the tendency for directional but variable growth in clones. Such variable growth calls into question adaptive interpretations based on deterministic models that utilize the mean values of growth parameters but ignore the highly variable nature of clonal growth.