BACKGROUND DNA barcoding, i.e. the use of a 648 bp section of the mitochondrial gene cytochrome c oxidase I, has recently been promoted as useful for the rapid identification and discovery of species. Its success is dependent either on the strength of the claim that interspecific variation exceeds intraspecific variation by one order of magnitude, thus establishing a "barcoding gap", or on the reciprocal monophyly of species. RESULTS We present an analysis of intra- and interspecific variation in the butterfly family Lycaenidae which includes a well-sampled clade (genus Agrodiaetus) with a peculiar characteristic: most of its members are karyologically differentiated from each other which facilitates the recognition of species as reproductively isolated units even in allopatric populations. The analysis shows that there is an 18% overlap in the range of intra- and interspecific COI sequence divergence due to low interspecific divergence between many closely related species. In a Neighbour-Joining tree profile approach which does not depend on a barcoding gap, but on comprehensive sampling of taxa and the reciprocal monophyly of species, at least 16% of specimens with conspecific sequences in the profile were misidentified. This is due to paraphyly or polyphyly of conspecific DNA sequences probably caused by incomplete lineage sorting. CONCLUSION Our results indicate that the "barcoding gap" is an artifact of insufficient sampling across taxa. Although DNA barcodes can help to identify and distinguish species, we advocate using them in combination with other data, since otherwise there would be a high probability that sequences are misidentified. Although high differences in DNA sequences can help to identify cryptic species, a high percentage of well-differentiated species has similar or even identical COI sequences and would be overlooked in an isolated DNA barcoding approach.

中文翻译：

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DNA条形码缺口是否存在？ - 蓝蝴蝶案例研究（鳞翅目：灰蝶科）。


背景DNA条形码，即线粒体基因细胞色素c氧化酶I的648bp片段的使用，最近被推广为可用于快速鉴定和发现物种。它的成功要么依赖于种间变异超过种内变异一个数量级的主张，从而建立“条形码差距”，要么依赖于物种的相互单系性。结果 我们对灰蝶科的种内和种间变异进行了分析，其中包括一个采样良好的进化枝（Agrodiaetus 属），该进化枝具有独特的特征：其大多数成员在核学上彼此不同，这有助于识别物种具有繁殖能力。即使在异域种群中也是孤立的单位。分析表明，由于许多密切相关的物种之间的种间差异较小，种内和种间 COI 序列差异范围存在 18% 的重叠。在邻接树剖面方法中，不依赖于条形码间隙，而是依赖于类群的综合采样和物种的互惠单系性，至少 16% 的剖面中具有同种序列的标本被错误识别。这是由于同种 DNA 序列的并系或多系可能是由不完整的谱系分类引起的。结论我们的结果表明，“条形码差距”是跨类群采样不足造成的。虽然DNA条形码可以帮助识别和区分物种，但我们提倡将其与其他数据结合使用，否则很可能会导致序列被错误识别。 尽管 DNA 序列的高度差异有助于识别隐秘物种，但高比例的分化良好的物种具有相似甚至相同的 COI 序列，在分离的 DNA 条形码方法中会被忽视。