from: Yellowstone Science 25(1)
by Colleen R. Detjens & Kellie J. CarimEnvironmental DNA (eDNA) is genetic material obtained from an environmental sample such as soil, sediment, water, or ice without directly handling the organism from which it originated (Thomsen and Willerslev 2015). This DNA is shed from the organism into the environment in a variety of forms, including skin cells, mucus, feces, or tissue. Biologists are able to collect this DNA and analyze it to determine the presence of specific species. In fact, this technique is so sensitive that even a single copy of DNA from an animal may be detected in an environmental sample. In recent years, eDNA-based sampling methods have become an increasingly common tool for wildlife managers. Within Yellowstone National Park (YNP), fisheries biologists have begun using eDNA from water samples to understand the distribution of various fish species. In collaboration with researchers at the National Genomics Center for Wildlife and Fish Conservation, located at the Forest Service Rocky Mountain Research Station in Missoula, Montana, we hope to contribute to the growing body of knowledge on the effectiveness and limitations of eDNA sampling as a monitoring tool. Applications and AnalysisThere are many potential benefits to collecting eDNA samples in conjunction with native fish restoration projects in YNP. Because eDNA sampling does not require fish be observed, biologists can survey waters without having to electrofish, handle, or stress fragile populations. The sensitivity of this tool may also allow biologists to detect invasive species while numbers are still low, which could prove invaluable to containing the spread of an invasion (Goldberg et al. 2013). The use of eDNA may also be helpful in determining the effectiveness of rotenone treatments to remove non-native fish from watersheds where native fish are being restored. Finally, biologists can use the amount of DNA in a sample to understand the relative abundance of a species at the landscape level (Takahara et al. 2012, Pilliod et al. 2013). In essence, eDNA samples provide a powerful snapshot in time for biologists to catalog information not on just one species, but potentially an entire biological community. LimitationsDespite the many benefits of using eDNA-based monitoring methods, there are still some limitations that can affect the accuracy of detecting a species. DNA that is free-floating in the environment will eventually degrade; factors such as temperature and exposure to ultraviolet light will speed the degradation process (Strickler et al. 2015). As a result, the further you are from a fish in the stream, the less likely you are to collect its DNA in a sample. Additionally, the rate at which fish shed DNA may not always be consistent and could be affected by conditions such as diet, temperature, and spawning activities (Klymus et al. 2015). Consequently, the ability of eDNA sampling to replace traditional methods of estimating species presence or abundance is not completely understood and, therefore, warrants further study. eDNA in Yellowstone National ParkWithin YNP, eDNA sampling was used to estimate the geographic extent of non-native Literature CitedGoldberg, C.S., A. Sepulveda, A. Ray, J. Baumgardt, and L.P. Waits. 2013. Environmental DNA as a new method for early detection of New Zealand mudsnails (Potamopyrgus antipodarum). Freshwater Science 32:792-800. |
Last updated: February 16, 2017