Patterns of clonal growth in Medeola virginiana and Solidago altissima.

摘要

Clonal plant species dominate many plant communities; thus they are of considerable ecological importance. Connected ramets within clones can function as physiological units, but there are few studies that identify either genetic individuals or connected groups of ramets. Clonal plants also have complicated life histories and growth forms: such complications have limited the number of theoretical studies on clonal plants. This thesis consists of empirical and theoretical studies designed to address these issues.; I identify Solidago altissima clone fragments in the field and I consider the population dynamic consequences of this information. I show that most ramet mortality is not true mortality; instead it is merely the loss of a piece of a genetic individual. I also show that size variation among S. altissima ramets is influenced little by the size of near neighbors, but is influenced by clonal factors.; I contribute to the the theory of clonal plants by developing models of vegetative spread for S. altissima and Medeola virginiana. For S. altissima, I document the morphological variation for clonal growth parameters, I analyze the clonal growth process with a suite of statistical tests, and I introduce and test random walk models, a new way to model the spread of clonal plants. My results indicate that clonal growth parameters are highly variable and are (statistically) independent across time. I also demonstrate that observed rates of clonal expansion are similar to random walk predicted values. These results suggest that deterministic models should not be used to describe the spread of S. altissima clones, but that the process of S. altissima clonal growth is consistent with stochastic simulation models and random walk models.; M. virginiana has been hypothesized to minimize competition among ramets by positioning ramets regularly in space. I develop a stochastic simulation model that indicates 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 of clonal growth.