Background Dragonflies and damselflies (Odonata) are important components in biomonitoring due to their amphibiotic lifecycle and specific habitat requirements. They are charismatic and popular insects, but can be challenging to identify despite large size and often distinct coloration, especially the immature stages. DNA-based assessment tools rely on validated DNA barcode reference libraries evaluated in a supraregional context to minimize taxonomic incongruence and identification mismatches. Methods This study reports on findings from the analysis of the most comprehensive DNA barcode dataset for Central European Odonata to date, with 103 out of 145 recorded European species included and publicly deposited in the Barcode of Life Data System (BOLD). The complete dataset includes 697 specimens (548 adults, 108 larvae) from 274 localities in 16 countries with a geographic emphasis on Central Europe. We used BOLD to generate sequence divergence metrics and to examine the taxonomic composition of the DNA barcode clusters within the dataset and in comparison with all data on BOLD. Results Over 88% of the species included can be readily identified using their DNA barcodes and the reference dataset provided. Considering the complete European dataset, unambiguous identification is hampered in 12 species due to weak mitochondrial differentiation and partial haplotype sharing. However, considering the known species distributions only two groups of five species possibly co-occur, leading to an unambiguous identification of more than 95% of the analysed Odonata via DNA barcoding in real applications. The cases of small interspecific genetic distances and the observed deep intraspecific variation in Cordulia aenea (Linnaeus, 1758) are discussed in detail and the corresponding taxa in the public reference database are highlighted. They should be considered in future applications of DNA barcoding and metabarcoding and represent interesting evolutionary biological questions, which call for in depth analyses of the involved taxa throughout their distribution ranges.

中文翻译：

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中欧和北欧蜻蜓 DNA 条形码参考的覆盖率和质量

背景蜻蜓和豆娘（蜻蜓目）是生物监测中的重要组成部分，因为它们的两栖生命周期和特定的栖息地要求。它们是具有魅力且受欢迎的昆虫，但尽管体型大且颜色通常不同，但识别起来可能具有挑战性，尤其是在未成熟阶段。基于 DNA 的评估工具依赖于在超区域环境中评估的经过验证的 DNA 条形码参考库，以最大限度地减少分类不一致和识别不匹配。方法 本研究报告了迄今为止对中欧蜻蜓目最全面的 DNA 条形码数据集的分析结果，其中包括 145 个记录的欧洲物种中的 103 个并公开存放在生命数据系统 (BOLD) 的条形码中。完整的数据集包括 697 个样本（548 个成年人，108 只幼虫）来自 16 个国家的 274 个地点，地理重点是中欧。我们使用 BOLD 生成序列差异度量，并检查数据集中 DNA 条形码簇的分类组成，并与 BOLD 上的所有数据进行比较。结果超过 88% 的物种可以使用它们的 DNA 条形码和提供的参考数据集轻松识别。考虑到完整的欧洲数据集，由于线粒体分化较弱和部分单倍型共享，12 个物种的明确鉴定受到阻碍。然而，考虑到已知的物种分布，只有两组五个物种可能同时出现，导致在实际应用中通过 DNA 条形码明确识别超过 95% 的分析的 Odonata。详细讨论了种间遗传距离小的情况和观察到的 Cordulia aenea (Linnaeus, 1758) 中的深层种内变异，并突出显示了公共参考数据库中的相应分类群。在 DNA 条形码和元条形码的未来应用中应考虑它们，并代表有趣的进化生物学问题，这需要在其分布范围内对所涉及的分类群进行深入分析。