A basin-scale application of environmental DNA assessment for rare endemic species and closely related exotic species in rivers: a case study of giant salamanders in Japan

1. To prevent the invasion of exotic species causing a decline in an endangered endemic species, it is important to determine the distribution of both species at an early stage, when the density of the exotic species is still low, and to manage the invasion immediately. However, distinguishing between closely related species is difficult because they share similar characteristics. 2. The identification of DNA fragments sampled from a body of water (environmental DNA) has become a popular technique for rapidly determining the distribution of a target species. In this study, we analysed environmental DNA in water samples from 37 sites across the Katsura River basin in Japan. We used TaqMan real-time PCR to distinguish the Japanese giant salamander Andrias japonicus from the closely related Chinese giant salamander Andrias davidianus, which is known to invade Japanese rivers and hybridize with the Japanese species. 3. In environmental samples, we detected mtDNA of the endemic species at 25...1. 为防止外来物种入侵导致濒危特有物种种群数量下降，需在外来物种种群密度仍处于较低水平的早期阶段，明确两类物种的分布范围并立即开展入侵防控工作。但由于亲缘关系相近的物种形态特征高度相似，二者的区分难度极大。2. 依托水体中提取的DNA片段——即环境DNA（environmental DNA）——开展物种分布快速检测，已成为当前主流的生态学调查技术。本研究采集了日本桂川流域37个采样点的水体样本，对其中的环境DNA进行分析；采用TaqMan实时荧光定量PCR（TaqMan real-time PCR）技术，对亲缘关系相近的日本大鲵（Andrias japonicus）与中国大鲵（Andrias davidianus）进行区分，其中中国大鲵已被证实会入侵日本河流并与日本大鲵发生杂交。3. 在本次环境样本中，我们于25个采样点检测到了该特有物种的线粒体DNA（mtDNA）……