The taxonomy of many groups of meiofauna is challenging due to their low number of diagnostic morphological characters and their small body size. Therefore, with the advent of molecular techniques that provide a new source of traits, many cryptic species have started to be discovered. Tardigrades are not an exception, and many once thought to be cosmopolitan taxa are being found to be complexes of phenotypically similar species. Macrobiotus pallarii Maucci, 1954 was originally described in South Italy and has been subsequently recorded in Europe, America, and Asia. This allegedly wide geographic range suggests that multiple species may be hidden under this name. Moreover, recently, genetic evidence to support this was put forward, and the Macrobiotus pallarii complex has been proposed to accommodate putative species related to M. pallarii. Here, we describe three new pseudocryptic species based on populations that would have been all classified as Macrobiotus pallarii if molecular methods were not employed. Using an integrative taxonomy approach, we analyzed animals and eggs from the topotypic population of Macrobiotus pallarii, together with four other populations of the complex. We recovered four distinct phylogenetic lineages that, despite the overlap of morphometric traits, can be separated phenotypically by subtle but discrete morphological characters. One lineage corresponds to Macrobiotus pallarii, whereas the other three are newly described as Macrobiotus margoae Stec, Vecchi & Bartels, sp. nov. from the USA, Macrobiotus ripperi Stec, Vecchi & Michalczyk, sp. nov. from Poland and Finland, and Macrobiotus pseudopallarii Stec, Vecchi & Michalczyk, sp. nov. from Montenegro. To facilitate species identification, we provide a dichotomous key for species of the M. pallarii complex. Delimitation of these pseudocryptic taxa highlights the need for an integrative approach to uncover the phylum’s diversity in full.

中文翻译：

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综合分类法解决了Macrobiotus pallarii复合体中的物种身份（Eutardigrada：Macrobiotidae）

许多小型动物群的分类具有挑战性，因为它们的诊断形态特征数量少且体型小。因此，随着提供新性状来源的分子技术的出现，许多神秘物种开始被发现。缓步动物也不例外，许多曾经被认为是世界性分类群的动物被发现是表型相似物种的复合体。Macrobiotus pallarii Maucci, 1954 最初在意大利南部被描述，随后在欧洲、美洲和亚洲都有记录。据称，这种广泛的地理范围表明，该名称下可能隐藏着多个物种。此外，最近提出了支持这一点的遗传证据，并且提出了 Macrobiotus pallarii 复合体来容纳与 M. pallarii 相关的假定物种。这里，我们描述了基于种群的三个新的假隐性物种，如果不采用分子方法，这些种群都会被归类为 Macrobiotus pallarii。使用综合分类法，我们分析了来自 Macrobiotus pallarii 拓扑种群的动物和鸡蛋，以及该复合体的其他四个种群。我们恢复了四个不同的系统发育谱系，尽管形态特征重叠，但可以通过微妙但离散的形态特征在表型上分开。一个谱系对应于 Macrobiotus pallarii，而其他三个被新描述为 Macrobiotus margoae Stec, Vecchi & Bartels, sp。十一月 来自美国，Macrobiotus ripperi Stec, Vecchi & Michalczyk, sp。十一月 来自波兰和芬兰，以及 Macrobiotus pseudopallarii Stec, Vecchi & Michalczyk, sp。十一月 来自黑山。为了便于物种识别，我们为 M. pallarii 复合体的物种提供了一个二分键。对这些假隐性分类群的界定突出表明需要一种综合方法来全面揭示该门的多样性。