The North American Bullfrog (Lithobates catesbeianus): Dispersal and Reservoir Potential of a Problematic Invasive Species in the Colorado Front Range

The anthropogenic introduction of species into new habitats is one of the leading factors driving declines in plant and animal populations across the globe. This is especially true of amphibians, as this group is currently considered the most threatened class of vertebrates on Earth. The North American bullfrog (Lithobates catesbeianus) is one such introduced species that has had devastating impacts on native amphibian communities in regions where it has been introduced. For my master\u27s thesis research, I synthesized information from field surveys, laboratory experiments, and geographic information to investigate the problematic North American bullfrog, L. catesbeianus, in the Colorado Front Range. Bullfrogs are considered an invasive species in the Colorado Front Range, and have been implicated in the decline of native amphibian species in this region. In my first chapter, I identified wetland-specific and landscape-level features that relate to the detection of bullfrog populations, and elucidated potential routes this species may use when moving across the Front Range landscape. In my second chapter, I clarified the role that bullfrogs may play in influencing the dynamics of the amphibian pathogen Batrachochytrium dendrobatidis (Bd) in this region. I developed specific criteria to determine if bullfrogs are more likely to act as a reservoir for Bd relative to other native amphibian hosts. By pairing field surveys with laboratory experiments, I determined that bullfrog populations fulfill these criteria and appear to be a reservoir for Bd in the Colorado Front Range. However, I also identified other native amphibian species that may be important reservoirs of Bd as well. By using data collected at multiple scales, this study also provides a unique insight into potential mechanisms that may be driving the patterns of Bd prevalence across differing amphibian communities. This research may facilitate the development of plans targeted at limiting North American bullfrog populations, and may help to inform management of the pathogen Bd in regions where this pathogen overlaps with bullfrog populations. Application of the results of this study can help to limit the spread of invasive species and disease, and may help mitigate the impact of these two important drivers of biodiversity loss