Presentation Title

Detection of California tiger salamanders (Ambystoma californiense): comparing eDNA and traditional net-based survey methods for maximum sensitivity

Faculty Mentor

Dr. Christy Wyckoff

Start Date

17-11-2018 2:00 PM

End Date

17-11-2018 2:15 PM

Location

C161

Session

Oral 3

Type of Presentation

Oral Talk

Subject Area

biological_agricultural_sciences

Abstract

California tiger salamanders are especially hard to survey since they spend the majority of their lives underground in mammal burrows, making the status of each population difficult to monitor. Despite this challenge in detection, it is well established that California tiger salamanders (Ambystoma californiense, CTS) are at risk due to several environmental factors–habitat destruction, hybridization with invasive salamanders (Ambystoma mavortium), and climatic changes in rainfall patterns. This project assesses the sensitivity and specificity of environmental-DNA (eDNA) detection for the California tiger salamander compared to the traditional capture-and-release methods using dip nets and seins. We performed field monitoring and sample collection at the Santa Lucia Preserve and Palo Corona Ranch Regional Ranch, Monterey Peninsula Regional Parks District, both located in Monterey County, CA using an integrated technique of visual surveys, protocol surveys, and eDNA sampling to assess perennial stock ponds for the presence or absence of California tiger salamanders. The eDNA experimental design includes a negative control (known CTS-negative pond), three known positive controls (reliable CTS-positive ponds), and seven ponds unlikely, but unconfirmed, to support CTS breeding. The eDNA detection of the California red-legged frog (Rana draytonii, CRLF) is used as a proxy for eDNA sensitivity. This study evaluates the efficacy of eDNA detection compared to traditional net-based surveys, correlation of net-based results and eDNA signal intensity, seasonality of CTS pond use, and the relationship between vegetation and detection success using traditional net surveys. Preliminary eDNA results show promise with increased sensitivity over net-based surveys and clean controls. Application of these methods to other sites could increase our confidence in presence-absence detection efforts, reduce sampling efforts and impacts, and improve conservation protections of vulnerable habitats.

Summary of research results to be presented

This study is the first experiment to investigate the sensitivity of environmental-DNA (eDNA) detection methods by comparing a newly-developed eDNA assay to traditional net-based surveys for the detection of California tiger salamanders (Californiense ambystoma). The goal of this study is to analyze these two methods for maximum sensitivity in the detection of this rare and cryptic species. Methods include field monitoring with visual and vegetation surveys, net-based surveys using seins and dip-nets, eDNA surveys that include sampling, processing, and testing with quantitative-polymerase chain reaction (qPCR). Aquatic, emergent, and surrounding pond vegetation coverage percentages were recorded and amphibian eggs, larvae, metamorphs, and adults were counted during visual and vegetation surveys. Environmental-DNA protocol from Goldberg lab at Washington State University was used for collecting water samples from ponds . This was a longitudinal study with bi-weekly sampling for two consecutive years. Cross-contamination was prevented by single-use, disposable equipment for sampling and processing. Each pond’s 250 mL sample was filtered through 5.0 micron polyethersulfone membrane filters and then tested at Goldberg lab using qPCR amplification and visualization techniques. Data from the last two years for both eDNA and net surveys was compared to investigate the sensitivity of each method. Results showed that eDNA demonstrated higher sensitivity in detection of California tiger salamanders than traditional net-based surveys. All three positive controls were repeatedly confirmed positive for the presence of California tiger salamanders with eDNA across the study, half of the unknown status ponds showed tiger salamander presence when net surveys showed species absence, and our negative controls–pond with no tiger salamander presence and distilled water samples–stayed constant throughout the entirety of the the study. The signal intensity for detecting California tiger salamanders with eDNA showed strong correlation with increases in rainfall and predicted breeding behavior.

This document is currently not available here.

Share

COinS
 
Nov 17th, 2:00 PM Nov 17th, 2:15 PM

Detection of California tiger salamanders (Ambystoma californiense): comparing eDNA and traditional net-based survey methods for maximum sensitivity

C161

California tiger salamanders are especially hard to survey since they spend the majority of their lives underground in mammal burrows, making the status of each population difficult to monitor. Despite this challenge in detection, it is well established that California tiger salamanders (Ambystoma californiense, CTS) are at risk due to several environmental factors–habitat destruction, hybridization with invasive salamanders (Ambystoma mavortium), and climatic changes in rainfall patterns. This project assesses the sensitivity and specificity of environmental-DNA (eDNA) detection for the California tiger salamander compared to the traditional capture-and-release methods using dip nets and seins. We performed field monitoring and sample collection at the Santa Lucia Preserve and Palo Corona Ranch Regional Ranch, Monterey Peninsula Regional Parks District, both located in Monterey County, CA using an integrated technique of visual surveys, protocol surveys, and eDNA sampling to assess perennial stock ponds for the presence or absence of California tiger salamanders. The eDNA experimental design includes a negative control (known CTS-negative pond), three known positive controls (reliable CTS-positive ponds), and seven ponds unlikely, but unconfirmed, to support CTS breeding. The eDNA detection of the California red-legged frog (Rana draytonii, CRLF) is used as a proxy for eDNA sensitivity. This study evaluates the efficacy of eDNA detection compared to traditional net-based surveys, correlation of net-based results and eDNA signal intensity, seasonality of CTS pond use, and the relationship between vegetation and detection success using traditional net surveys. Preliminary eDNA results show promise with increased sensitivity over net-based surveys and clean controls. Application of these methods to other sites could increase our confidence in presence-absence detection efforts, reduce sampling efforts and impacts, and improve conservation protections of vulnerable habitats.