DNA barcode sheds light on species boundaries in the common morphologically variable rove beetle <i>Quedius umbrinus</i>-complex that puzzled taxonomists for more than a century (Coleoptera, Staphylinidae)

In the course of a long taxonomic history, <i>Quedius umbrinus</i> Erichson, a common West Palaearctic rove beetle, was gradually split into a dozen species before all of them, except <i>Q. sigwalti</i> Coiffait from Crete, were lumped back into a single species again. All these shifts were based on the intuitive evaluation of morphological variation only. We sequenced the barcoding fragment of the CO1 gene across specimens of <i>Q. umbrinus</i>-complex broadly covering its geographic range and performed several DNA barcode species delimitation analyses on this dataset: tree-based Bayesian inference and Maximum likelihood, as well as tree-independent character-based (PTP, GMYC) and distance-based (ABGD). Molecular clades were largely congruent among all analyses and revealed four candidate species lineages. Of them, only <i>Q. sigwalti</i> is easy to distinguish by morphology alone. Morphological differences between other candidate species are present, but they are weak and do not hold for all specimens. To reflect new data in the classification we reinstated <i>Q. pseudoumbrinus</i> Lohse (stat. res.) as a species even though it is not always distinct from <i>Q. umbrinus</i> Er. (stat. rev.) morphologically. Also, we described a new species <i>Q. volkeri</i> (sp. nov.) from the north-western Caucasus. Finally, we placed <i>Q. angaricus</i> Coiffat in synonymy with <i>Q. pseudoumbrinus</i> Lohse (syn. nov.). http://www.zoobank.org/urn:lsid:zoobank.org:act:B6E2ED11-2029-48E7-975F-060D9DA61648

在漫长的分类学研究历程中，西古北界常见的隐翅虫*Quedius umbrinus* Erichson曾被逐步划分为十余个物种，最终除来自克里特岛的*Q. sigwalti* Coiffait外，其余类群均被重新归并为单一物种。上述所有分类变动均仅基于形态变异的主观评估。我们对广泛覆盖其地理分布范围的*Q. umbrinus*复合群标本开展了CO1基因条形码片段的测序，并基于该数据集完成了多项DNA条形码物种界定分析：基于系统发育树的贝叶斯推断与最大似然分析，以及非基于系统发育树的特征分析法（PTP、GMYC）与距离分析法（ABGD）。所有分析得到的分子支系大体一致，共揭示了4个候选物种谱系。其中仅*Q. sigwalti*可仅凭形态特征轻松区分。其余候选物种间虽存在形态差异，但差异微弱且并非在所有标本中均稳定存在。为在分类系统中体现新的研究数据，我们恢复了*Q. pseudoumbrinus* Lohse的物种地位（stat. res.，即恢复原级），尽管其形态特征并非总能与*Q. umbrinus* Er.（stat. rev.，即修订原级）区分开来。此外，我们还描述了来自高加索西北部的新物种*Q. volkeri*（sp. nov.，即新种）。最后，我们将*Q. angaricus* Coiffat定为*Q. pseudoumbrinus* Lohse的新异名（syn. nov.）。http://www.zoobank.org/urn:lsid:zoobank.org:act:B6E2ED11-2029-48E7-975F-060D9DA61648