Thesis
American bullfrog (Lithobates catesbeianus) invasion in California
Washington State University
Master of Science (MS), Washington State University
12/2020
DOI:
https://doi.org/10.7273/000004205
Handle:
https://hdl.handle.net/2376/125059
Abstract
Invasive species have far-reaching ecological and economic impacts. The American bullfrog (Lithobates catesbeianus) has spread globally through anthropogenic activity and has been named one of the world's worst invasive species. Bullfrogs have especially impacted native amphibians in California through predation, competition, and disease. Bullfrogs are thought to be expanding in the state and may be able to impact additional amphibians that have already undergone severe disease-related declines. With the current projects, I used environmental niche models (ENMs) to examine the patterns and drivers underlying historic bullfrog invasion in California. This exercise allowed me to identify potentially suitable habitats that are at risk of future invasion. I also built multi-scale occupancy models using detections from environmental DNA (eDNA) samples to examine the potential of Sierra Nevada meadow restoration projects to promote regional occupancy of bullfrogs and the amphibian chytrid fungus (Batrachochytrium dendrobatidis, Bd). Bullfrogs have spread in a diffuse pattern from their earliest introduction points in California, and the Klamath mountains and southern Coast range may be invaded in the future. However, bullfrogs appear to be limited from high elevation habitats in the Sierra Nevada, possibly due to winter freezing or topographic resistance. Site-level occupancy of bullfrogs and Bd did not differ between Sierra Nevada meadows restored with different methods, but the quantity of bullfrog eDNA detected tended to be highest at pond-and-plug restored meadows. Bd eDNA quantity was also positively influenced by the presence of bullfrogs within the meadow. Even limited overlap between bullfrogs and sensitive native amphibians in the future could increase the transmission of Bd. Future work should focus on the local invasion dynamics of bullfrogs in areas occupied by sensitive amphibians as well as spatio-temporal patterns in the prevalence of Bd, both in the environment and in amphibian hosts.
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Details
- Title
- American bullfrog (Lithobates catesbeianus) invasion in California
- Creators
- Nicolette Leighana Nelson
- Contributors
- Jonah Piovia-Scott (Advisor) - Washington State University, Biological Sciences, School of
- Awarding Institution
- Washington State University
- Academic Unit
- Biological Sciences, School of
- Theses and Dissertations
- Master of Science (MS), Washington State University
- Publisher
- Washington State University
- Identifiers
- 99900896437501842
- Language
- English
- Resource Type
- Thesis