Conservation Ecology Center, Smithsonian Conservation Biology Institute, Front Royal, Virginia, United States of America.
Center for Conservation Genomics, Smithsonian Conservation Biology Institute, Washington, DC, United States of America.
PLoS One. 2019 Apr 24;14(4):e0215586. doi: 10.1371/journal.pone.0215586. eCollection 2019.
Environmental DNA (eDNA) has been used to record the presence of many different organisms in several different aquatic and terrestrial environments. Although eDNA has been demonstrated as a useful tool for the detection of invasive and/or cryptic and declining species, this approach is subject to the same considerations that limit the interpretation of results from traditional survey techniques (e.g. imperfect detection). The wood turtle is a cryptic semi-aquatic species that is declining across its range and, like so many chelonian species, is in-need of a rapid and effective method for monitoring distribution and abundance. To meet this need, we used an eDNA approach to sample for wood turtle presence in northern Virginia streams. At the same time, we used repeat visual encounter surveys in an occupancy-modelling framework to validate our eDNA results and reveal the relationship of detection and occupancy for both methods. We sampled 37 stream reaches of varying size within and beyond the known distribution of the wood turtle across northern Virginia. Wood turtle occupancy probability was 0.54 (0.31, 0.76) and while detection probability for wood turtle occupancy was high (0.88; 0.58, 0.98), our detection of turtle abundance was markedly lower (0.28; 0.21, 0.37). We detected eDNA at 76% of sites confirmed occupied by VES and at an additional three sites where turtles were not detected but were known to occur. Environmental DNA occupancy probability was 0.55 (0.29, 0.78); directly comparable to the VES occupancy estimate. Higher probabilities of detecting wood turtle eDNA were associated with higher turtle densities, an increasing number of days since the last rainfall, lower water temperatures, and lower relative discharges. Our results suggest that eDNA technology holds promise for sampling aquatic chelonians in some systems, even when discharge is high and biomass is relatively low, when the approach is validated and sampling error is quantified.
环境 DNA（eDNA）已被用于记录许多不同水生和陆地环境中不同生物的存在。虽然 eDNA 已被证明是一种用于检测入侵和/或隐匿和衰退物种的有用工具，但这种方法受到限制结果解释的相同考虑因素的限制，例如不完全检测。木龟是一种隐匿的半水生物种，其分布范围正在缩小，与许多龟类物种一样，需要一种快速有效的方法来监测其分布和丰度。为了满足这一需求，我们使用 eDNA 方法在弗吉尼亚州北部的溪流中采样木龟的存在。同时，我们在占有模型框架中使用重复的视觉接触调查来验证我们的 eDNA 结果，并揭示两种方法的检测和占有之间的关系。我们在弗吉尼亚州北部的已知木龟分布范围内和范围外的 37 个溪流流域中进行了采样。木龟的占有概率为 0.54（0.31，0.76），而木龟占有检测概率较高（0.88；0.58，0.98），但我们对龟类丰度的检测明显较低（0.28；0.21，0.37）。我们在 76%的经 VES 确认的木龟栖息地中检测到了 eDNA，在另外三个没有检测到木龟但已知存在的地点也检测到了 eDNA。环境 DNA 的占有概率为 0.55（0.29，0.78）；与 VES 占有估计值直接可比。检测到木龟 eDNA 的概率较高与龟类密度较高、上次降雨后天数增加、水温较低以及相对流量较低有关。我们的结果表明，即使在排放高且生物量相对较低的情况下，当方法得到验证且采样误差被量化时，eDNA 技术在某些系统中对水生龟类的采样具有很大的潜力。
