The original diversity of Pelophylax water frogs has been compromised by multiple biological invasions all over Western Europe. For the European pool frog (P. lessonae), the Joux Valley—a 30 km highland depression in northwestern Switzerland—stands as the last stronghold spared by exotic lineages. In order to manage P. lessonae in the valley, we combined traditional field surveys with environmental DNA metabarcoding and mapped the regional distribution of amphibian species. Both approaches concurred that P. lessonae persists at a single isolated site (Pontet). Continuous monitoring of this population throughout the spring and summer 2019 informed on their wintering quarters (most likely the forest litter immediately surrounding the breeding pond), as well as the timing of migration (end of April), breeding (June), and larval development (June–August). In parallel, we experimented the first use of drone technology for amphibian surveillance: 30 adults were individually counted during an aerial survey at the peak of the breeding season, confirming the small size of the population. Finally, we compared some biotic and abiotic properties among water bodies throughout the valley and flagged a few sites that were ecologically similar to Pontet. In a landscape dominated by pastoral activities where Pelophylax dispersal is virtually impossible, these could be candidates for future translocation efforts. Our study illustrates the application of next-generation monitoring techniques for the urgent management of threatened species and stresses the need for reevaluating the conservation status of P. lessonae in Western Europe, where it appears to subsist in low numbers at one last locality.

中文翻译：

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监测西欧本地池蛙的最后据点（Pelophylax lessonae）及其保护意义

在整个西欧，多种生物入侵已破坏了凤尾水蛙的原始多样性。对于欧洲池蛙（P. lessonae），瑞士西北部30公里高地洼地的乔克斯谷（Joux Valley）是最后一个被外来血统幸存的据点。为了管理山谷中的P. lessonae，我们将传统的野外调查与环境DNA元条形码相结合，并绘制了两栖动物物种的区域分布图。两种方法都同意P. lessonae保留在一个孤立的站点（Pontet）。在2019年春季和夏季期间，对该种群进行持续监测，了解了它们的越冬季度（很可能是繁殖池周围的森林凋落物），以及迁徙的时间（4月底），繁殖（6月）和幼体发育（6月至8月）。同时，我们试验了无人机技术首次用于两栖动物监视的过程：在繁殖季节的高峰期进行的空中调查中，分别对30名成年动物进行了计数，从而确认了种群的规模。最后，我们比较了整个山谷水体之间的某些生物和非生物特性，并标记了一些与庞特生态相似的地点。在景观牧区活动，其中占主导地位黑斑侧褶分散几乎是不可能的，这些可能是未来迁移工作的候选者。我们的研究说明了下一代监测技术在受威胁物种的紧急管理中的应用，并强调有必要重新评估西欧的小白僵菌的保护状况，该物种在最后一个地方似乎数量很少。