Thesis
Landscape-Scale Application of Paired Edna and Field Surveys for the Detection of At-Risk Wetland Amphibians
Washington State University
Master of Science (MS), Washington State University
2023
DOI:
https://doi.org/10.7273/000005232
Abstract
Amphibians are the most threatened of the vertebrate groups and population declines have been directly influenced by wetland removal, conversion, or alteration. Due to these threats, it is imperative to understand the region-wide distributions of imperiled wetland amphibians and implement effect surveys to inform management actions. Environmental DNA (eDNA) sampling is an emerging survey method that is effective at detecting low-density and patchily distributed amphibians and many eDNA studies have demonstrated high detection probabilities for rare amphibians; however, most of these studies were conducted within a relatively small area, limiting the amount of variation in survey sites. Therefore, eDNA survey methods have room for refinement when understanding eDNA detection success across a wide variety of wetlands while also incorporating this knowledge into survey design. We compared a spatially informed eDNA sampling protocol to field surveys across two seasons (2021 and 2022) to detect the Santa Cruz long-toed salamander (SCLTS), the California tiger salamander (CTS), and the California redlegged frog (CRLF), across freshwater wetlands in the Monterey Bay area, California. We constructed a Bayesian hierarchical multi-species occupancy model to identify environmental and habitat variables that could influence species occupancy and eDNA detections. We found high per sample detection probabilities using our eDNA sampling design for the SCLTS, CTS, and CRLF (0.75, 0.96, and 0.89, respectively) and had non-detections at only 5 sites where the species was detected by field methods. We found that the proportion of inhibited samples at a wetland was negatively associated with SCLTS detection probabilities but did not detect an influence of other environmental factors that are known to degrade eDNA or influence eDNA detection success. Finally, we analyzed habitat variables that could influence sample inhibition in a generalized linear model and found that the proportion of floating vegetation covering a wetland site was positively associated with the probability of sample inhibition. This study demonstrates that this eDNA sampling protocol is ready for field implementation to detect these at-risk amphibians across the variety of wetlands where they occur and is also likely to be highly effective for detecting other wetland species.
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Details
- Title
- Landscape-Scale Application of Paired Edna and Field Surveys for the Detection of At-Risk Wetland Amphibians
- Creators
- Mitchell James Ralson
- Contributors
- Caren S Goldberg (Advisor)Jesse L. Brunner (Committee Member)Jenifer McIntyre (Committee Member)Christy Wyckoff (Committee Member)
- Awarding Institution
- Washington State University
- Academic Unit
- Environment, School of the (CAHNRS)
- Theses and Dissertations
- Master of Science (MS), Washington State University
- Publisher
- Washington State University
- Number of pages
- 60
- Identifiers
- 99901019634201842
- Language
- English
- Resource Type
- Thesis