Data from: Spatial and temporal patterns of environmental DNA detection to inform sampling protocols in lentic and lotic systems

The development of efficient sampling protocols for the capture of environmental DNA (eDNA) could greatly help improve accuracy of occupancy monitoring for species that are difficult to detect. However, the process of developing a protocol in situ is complicated for rare species by the fact that animal locations are often unknown. We tested sampling designs in lake and stream systems to determine the most effective eDNA sampling protocols for two rare species: the Sierra Nevada yellow-legged frog (Rana sierrae) and the foothill yellow-legged frog (R. boylii). We varied water volume, spatial sampling, and seasonal timing in lakes and streams; in lakes we also tested multiple filter types. We found that filtering 2 L versus 1 L increased the odds of detection in streams 5.42X (95% CI: 3.2-9.19X) in our protocol, from a probability of 0.51 to 0.85 per technical replicate. Lake sample volumes were limited by filter clogging and we found no effect of volume or filter type. Sampling later in the season increased the odds of detection in streams by 1.96X for every 30 days (95% CI: 1.3 - 2.97X) but there was no effect for lakes. Spatial autocorrelation of the quantity of yellow-legged frog eDNA captured in streams between 100 and 200 m, indicating that sampling at close intervals is important.

开发用于捕获环境DNA（eDNA）的高效采样方案，可显著提升难以检测物种的占据监测准确率。然而，针对稀有物种开展原位采样方案开发的过程却颇为复杂，原因在于目标动物的栖息位置通常难以确定。本研究在湖泊与溪流系统中测试了多种采样设计，旨在为两种稀有物种——内华达山脉黄腿蛙（*Rana sierrae*）与山麓黄腿蛙（*R. boylii*）——确定最优的eDNA采样方案。我们在湖泊与溪流中分别设置了不同的水样体积、空间采样策略与季节采样时间梯度；针对湖泊样本，我们还测试了多种滤膜类型。研究结果显示，在本研究的采样方案中，溪流样本采用2L滤水体积相较于1L，可将单次技术重复的检出优势提升5.42倍（95%置信区间：3.2~9.19倍），单次技术重复的检出概率从0.51提升至0.85。湖泊样本的滤水体积受滤膜堵塞限制，且未观察到采样体积或滤膜类型对检出效果的显著影响。季节延后采样可使溪流样本的检出优势每30天提升1.96倍（95%置信区间：1.3~2.97倍），但该效应在湖泊样本中未显现。本研究观察到，溪流中100~200米范围内捕获的黄腿蛙eDNA含量存在空间自相关性，这表明采用较近的采样间隔至关重要。