The proposed research will address the evolutionary dynamics of colonization in newly-founded populations of Lupinus lepidus var. lobii, an important plant colonist of the blast zone at Mt. Saint Helens. Preliminary data indicate that these populations are genetically differentiated from each other over small spatial scales. The scale and magnitude of this differentiation will be documented, and the ecological and demographic factors which may affect future differentiation will be studied. Measurements of population growth rate, age structure, seedbank dynamics, and outcrossing rates will be made in different aged populations, and in artificial founder populations. These parameters and genetic data will allow estimation of a key evolutionary parameter, effective population size, and its rate of growth after a population bottleneck. Gene flow between populations will be measured using genetic data for small populations. Effective size, gene flow, and estimates of patch turnover will be incorporated in simulations of metapopulation genetic models. Finally, the potential for stochastic differentiation will be compared to results from transplant experiments designed to elucidate the magnitude of and spatial variation in selection pressures. This research will provide insight into the relative importance of drift and selection during the founding of populations, and information of central value in understanding the recovery of naturally or artificially damaged ecological systems.
