The largest apochelan genus, Milnesium, is increasingly gaining attention. However, our knowledge on the phylogeny of Milnesiidae is strongly limited. In fact, so far, apochelan species usually served only as outgroups in phylogenetic analyses of other tardigrade groups. Thus, the goal of this study was to reconstruct the first multilocus molecular phylogeny of Milnesium and test several hypotheses on the evolution and dispersion of species in the genus by mapping taxonomically important morphological traits, reproductive mode and geographic distribution onto the phylogenetic tree. The phylogeny was inferred from four DNA markers (nuclear 18S rRNA, 28S rRNA, ITS2 and mitochondrial COI) and for 34 populations representing 25 species collected across the globe. Phylogenetic analysis revealed distinct molecular lineages within the genus, but rather than by morphological characters, species clustered by zoogeographic zones. In fact, no obvious patterns of phenotypic traits or reproductive mode were observed, which may indicate high levels of convergent evolution in morphology throughout the genus. The lack of congruence between morphology and phylogeny did not allow splitting this largest apochelan genus into separate taxonomic units such as genera or subgenera. On the other hand, the correlation between phylogeny and geography may suggest limited dispersal of at least some Milnesium species.

中文翻译：

---

Milnesium（Tardigrada）属的第一个广泛的多基因位系统发育揭示遗传标记和形态性状之间没有一致性

最大的无足动物属（Milnesium）越来越受到关注。但是，我们对Milnesiidae的系统发育的认识受到严格限制。实际上，到目前为止，在其他缓坡类群的系统发育分析中，阿朴类物种通常仅作为外群。因此，本研究的目的是通过将分类学上重要的形态学特征，生殖方式和地理分布图绘制到系统树上，从而重建米尔尼斯的第一个多基因座分子系统发育，并测试关于属中物种进化和分散的几种假设。系统发育由四个DNA标记（核18S rRNA，28S rRNA，ITS2和线粒体COI推断）），代表了全球25个物种的34个种群。系统发育分析揭示了该属内不同的分子谱系，但不是按形态学特征而是由动物地理区域聚集的物种。实际上，没有观察到明显的表型性状或生殖方式，这可能表明整个属的形态学都在高度收敛。形态和系统发育之间缺乏一致性，因此无法将这个最大的无足动物属划分为不同的分类单位，例如属或亚属。另一方面，系统发育和地理之间的相关性可能表明至少某些米尔尼斯物种的扩散有限。