Geospatial characteristics such as isolation and avenues of connectivity influence an invader's pattern of dispersal and distribution. However many examinations of invasion success ignore the contribution of dispersal to patterns of invasion and focus only on the local environmental/habitat factors. This study examines the interaction of geospatial characteristics, that may influence dispersal, and local environmental factors, that may govern successful occupation, on the likelihood of invasion (invasability) of wetlands within an agriculturally modified landscape. I examined the current invasion of seasonal wetlands in south-central Florida ranchland by non-native apple snails (Pomacea maculata (Ampullariidae)) as a model system for understanding this interaction. I surveyed spatial occurrence of P. maculata in 171 wetlands in 2014 and found they occurred in 43% of wetlands surveyed. I evaluated how occurrence was related to geospatial variables (proximity to propagule sources, shoreline complexity, interwetland distance, elevation, area and ditch presence) and wetland characteristics (pH, water hardness, conductivity and soil type) for 95 wetlands. Presence of ditch connections and more neutral water pH were associated with P. maculata occurrence. I did not find evidence that Euclidean distance and minimum ditch distance were associated with P. maculata occurrence. I also performed a 5 month field experiment where I translocated snails to previously occupied and non-occupied wetlands and measured snail survival and growth (20 wetlands from November to March). This experiment evaluated if non-occurrence during survey was more likely to be associated with unfavorable habitat conditions or dispersal limitation. Wetland pH and water hardness explained variation in P. maculata survival, and wetland pH best explained growth. I did not find evidence that prior occupancy affected the snail survival and growth, which suggests previously unoccupied wetlands are due to dispersal limitation. These results emphasize that man-made conduits can increase permeability of the landscape, facilitating the dispersal and introduction of nonnative species and the need for the inclusion of dispersal metrics in understanding invasive species distribution.
Master of Science (M.S.)
College of Sciences
Length of Campus-only Access
Masters Thesis (Open Access)
Pierre, Steffan, "Does the Journey Matter More Than the Destination? The Contribution of Geospatial and Local Conditions to Invasive Pomacea Maculata Distribution Across Ranchland Wetlands" (2015). Electronic Theses and Dissertations. 5153.