Spatial Ecology and Invasion Dynamics of Burmese Pythons in South Florida
Predicting the geographic spread of invasive species is central to the design of effective control and management efforts. Most invasive species spread modeling is fundamentally phenomenological and focused on predicting rates based on patterns without understanding the basis of those patterns. There is a clear need for more mechanistic insight into constraints on biological invasions. Traditional models of species spread often ignore complexity in the movement behavior of the species and simplify landscape composition in an effort to increase mathematical tractability. Individual-based modeling can incorporate variation and complexity in movement strategies to improve predictions of species spread and yield insight into traits influencing invasive potential. The Burmese python (Python molurus bivittatus), a native of southern Asia, is established in South Florida and is currently expanding its range northward through the Florida peninsula and southward into the Florida Keys. Movement rates of Burmese pythons are among the highest documented for any species of snake, and recent evidence suggests that these snakes have sophisticated, large-scale navigational capacity. Because of Burmese pythons’ complexity in movement behavior and navigational ability, traditional models of spatial spread ma
y be unable to generate predictions useful to control or containment efforts. I use a combination of field experiments and modeling to determine the influence of movement behavior on spread dynamics. I conduct observational studies of free-ranging juvenile pythons and controlled experiments of juvenile python sensory and navigational ability. I use spatially-explicit, individual-based models that incorporate variation in movement in real landscapes to provide informative predictions of spread rate and invasion routes. Specifically, I determine the influence of movement behavior, navigational ability, and sensory capacity to spread dynamics of Burmese pythons. This research provides insight into factors influencing the dynamics of the geographic spread of species, with implications for invasive species control, prediction of species’ range shifts resulting from climate change, the spatial dynamics of species in changing landscapes, and a mechanistic understanding of observed species’ ranges.
Movement Ecology of Juvenile Pond-breeding Amphibians
Human-induced habitat change is widely regarded as a primary factor threatening the persistence of species. One major consequence of habitat alteration is its effect on the movement behavior of individuals. Animal movement is often strongly influenced by habitat type; knowledge of the strength, direction, and variation inherent in species’ behavioral reactions to novel or altered habitat is crucial for identifying the mechanistic causes of population or metapopulation dynamics, and for maximizing the effectiveness of conservation and management practices. Natal dispersal is an important mechanism by which species mitigate the effects of unpredictable variation in the spatial distribution of resources and is critical to many species’ spatial dynamics. Habitat alteration impacts the spatial patterning of resources and the risks associated with searching for resources.. I use a combination of empirical studies of juvenile amphibian movement and individual-based modeling to investigate the influence of habitat amount and arrangement on the persistence of pond-breeding amphibian populations.
Davidson undergraduate Katie Greene is currently studying the impacts of conspecific cues on settlement behavior in juvenile spotted salamanders (Ambystoma maculatum). She is additionally building individual-based models in Netlogo to simulate salamander dispersal patterns in the presence of conspecific trailing.
Factors Affecting Bog Turtle Survival in North Carolina
Davidson student Annalee Tutterow is studying variation in survivorship of NC bog turtle populations in collaboration with the NC Wildlife Research Commission, the Catawba Lands Conservancy, and Project Bog Turtle (non-profit).
Management Strategies for Mitigating Spread of Exotic Biofuel Crops
Herbaceous perennial crops are becoming a larger component of bioenergy production both in the United States and worldwide. However, there is growing concern that perennial crops pose a substantial risk of biological invasion as a result of the same traits that make them ideal for bioenergy production: low nutrient requirements, fast growth, and drought and cold tolerance. Miscanthus x giganteus is a sterile perennial grass native to Asia which generates high fuel yield even in northerly latitudes. Because of its low nutrient requirements, M. x giganteus has been proposed as an ideal biofuel crop to be planted in marginal lands unfit for food production in the northern US. A fertile variety of M. x giganteus was developed in an effort to decrease the costs associated with planting rhizomes of the sterile variety. However, there are currently no management recommendations required by the EPA to limit the probability of spread of the fertile variety outside of planted fields. We implemented a spatially-explicit population model of fertile M. x giganteus to determine the efficacy of different proposed management strategies on limiting or slowing the spread of this species. Results of this model illustrate the landscape-scale consequences of fertile M. x giganteus and suggest that the negative effects of an invasion may outweigh the benefits of decreased input costs to farmers. Maximizing the net benefits of biofuels may entail planting species with either low dispersal capacity or species for which spread outside of planted fields is not problematic.