Expansion of the known distribution of the coastal tailed frog, Ascaphus truei, in British Columbia, Canada, using robust eDNA detection methods

PLoS One. 2019 Mar 14;14(3):e0213849. doi: 10.1371/journal.pone.0213849. eCollection 2019.

Abstract

The coastal tailed frog (Ascaphus truei) is endemic to the Pacific Northwest of North America and is listed as a species of Special Concern under the Canadian Species at Risk Act. Its range is limited to British Columbia where it occurs widely west of the Coast Mountain Ranges extending north almost to the Alaskan Panhandle. The present study focused on surveying within the Cayoosh, Bridge (Shulaps), Seton, Anderson, Carpenter, and Downton Lake drainages. Four years of previous inventory efforts using conventional time-constrained search (TCS) methods detected tailed frog at 23/292 discrete sites (7.9% detection rate) in seven watersheds. Non-invasive environmental DNA (eDNA) methods hold promise for cryptic and low-abundance species detection. We rigorously validated a quantitative real-time polymerase chain reaction (qPCR)-based tool for detecting coastal tailed frog eDNA in water samples. This eASTR4 test is highly specific and sensitive. We applied a two-step targeted eDNA analysis approach on duplicate filtered water samples from a total of 72 sites collected over five days. The first IntegritE-DNA step mitigates false negative results and tests all DNA samples for the ability to support amplification from endogenous plant chloroplast DNA as a measure of sample viability. Three DNA samples failed this step even after inhibitor clean up suggesting that these samples were poor quality and not reliable for targeted species' DNA analyses. All other DNA samples were deemed viable and were then tested for species-specific DNA. Coastal tailed frog eDNA was detected in 55/72 (76%) discrete stream reaches; nine sites with historical known occurrence were all eDNA positive. The false negative rate for TCS compared to eDNA methods was 58%. The results expand known coastal tailed frog distribution to 24 watersheds effectively more than tripling extant occurrences and confirm a previously suspected, apparently isolated coastal tailed frog metapopulation in the Shulaps drainage.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animal Distribution*
  • Animals
  • Anura / classification
  • Anura / genetics*
  • British Columbia
  • DNA / analysis*
  • DNA / genetics*
  • Ecosystem
  • Environmental Monitoring / methods*
  • Genetics, Population*
  • Species Specificity

Substances

  • DNA

Grants and funding

This work was supported by the Fish and Wildlife Compensation Program (FWCP) and the BC Ministry of Environment and Climate Change Strategy through the Land-based Investment Strategy (LBIS). FWCP program partners include BC Hydro, the Province of BC, Fisheries and Oceans Canada, First Nations and the public; working together to conserve and enhance fish and wildlife impacted by the construction of BC Hydro dams. The funders did not play a role in the study design, data collection or analysis, decision to publish, or preparation of the manuscript and only provided financial support in the form of research materials. JH is an employee of Hemmera Envirochem Inc. who provided support in the form of salary for JH, but did not have any additional role in the study design, data collection and analysis, decision to publish, or preparation of the manuscript. The specific roles of the authors are articulated in the “Author contributions” section.