Freshwater ecosystems are the most vulnerable worldwide and freshwater bivalves rank amongst the most threatened animals in the world. Surveying and monitoring freshwater bivalves are difficult tasks: they are difficult to find, hard to identify (taxonomic expertise is needed), and working underwater is technically challenging. It is therefore crucial to find more efficient methods to survey and monitor these species. Here, we present the first metabarcoding approach for freshwater bivalves and compare environmental DNA (eDNA) and traditional surveys. We describe two sets of primers (for Unionida and Venerida) developed for freshwater bivalves eDNA metabarcoding. These primers have been tested in the field, with about 300 studied sites. Results were compared to freshwater bivalves’ surveys using traditional methods, with eDNA always detecting more species than traditional surveys, especially when Sphaerids were taken into account. While our study initially focused on Western Palearctic freshwater bivalve species, our primers were confronted in silico with available sequences and have proven to be effective at a global scale. The results show that eDNA metabarcoding, with our developed primers, is a remarkable tool allowing for non-invasive surveys, detection of rare and inconspicuous species, absence data and overall freshwater bivalves routine monitoring.

中文翻译：

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淡水双壳类生物多样性评估的环境 DNA 元条形码：西古北区（欧洲次区域）的方法和结果

淡水生态系统是世界上最脆弱的生态系统，淡水双壳类动物是世界上受威胁最严重的动物之一。淡水双壳类的调查和监测是一项艰巨的任务：它们很难找到，很难识别（需要分类学专业知识），而且在水下工作在技术上具有挑战性。因此，找到更有效的方法来调查和监测这些物种至关重要。在这里，我们介绍了淡水双壳类动物的第一种元条形码方法，并比较了环境 DNA (eDNA) 和传统调查。我们描述了为淡水双壳类 eDNA 元条形码开发的两组引物（用于 Unionida 和 Venerida）。这些引物已经在现场进行了测试，大约有 300 个研究位点。结果与使用传统方法的淡水双壳类调查进行了比较，与传统调查相比，eDNA 总是能检测到更多的物种，尤其是当考虑到球虫时。虽然我们的研究最初侧重于西部古北淡水双壳类物种，但我们的引物在计算机上面对可用序列，并已被证明在全球范围内是有效的。结果表明，带有我们开发的引物的 eDNA 元条形码是一种出色的工具，可用于非侵入性调查、检测稀有和不显眼的物种、缺失数据和整体淡水双壳类常规监测。