SPATIAL MODELING OF A REALIZED NICHE: THE INVASION OF FENNEL INTO COASTAL HABITATS OF VIRGINIA'S EASTERN SHORE
Kathryn MacCormick, Matthias Leu.
College of William and Mary, Williamsburg, VA.
Establishment is an important phase in the invasion process during which an exotic species escapes cultivation and successfully survives and reproduces in its new habitat, ultimately becoming naturalized and potentially invasive in its new range. One of the earliest cultivated plants, sweet fennel (Foeniculum vulgare Mill.) has gained a global distribution due to anthropogenically mediated dispersal; it alters vegetative structure and function by forming dense stands and threatens invasion into coastal shrub and grassland habitats worldwide. Like many Mediterranean species adapted to disturbed habitats, fennel produces numerous small seeds that are capable of forming a persistent seedbank. The interaction of dispersal, anthropogenic disturbance, and competition for suitable micro-habitat sites in a species that is on the verge of regional invasion make Virginiaâ€™s eastern shore an interesting system for studying the invasion process. By modeling the distribution of fennel vegetation and seedbank at the eastern shore of the Virginia National Wildlife Refuge, we are investigating the dispersal mechanisms, anthropogenic activities, and abiotic conditions that are contributing to fennelâ€™s success. We will conduct field surveys of fennel stem and seed densities with a stratified sampling design which will account for distance to anthropogenic features and refuge management methods. Using spatially applied statistical models and information theory, we will estimate the relative influence of multiple environmental and site variables to explain fennel occurrence. Preliminary observations suggest that proximity to roads and certain mowing methods may be important factors which could have management implications for future roadside mowing programs.