Kinorhyncha is a phylum of microscopic, benthic marine invertebrates found throughout the world, from the Arctic to Antarctica and from the intertidal zone to the deep sea. Within the most species-rich genus, Echinoderes, we find a putatively monophyletic species group, the so-called Echinoderes coulli-group. The remarkable morphological similarities of the E. coulli-group species and the fact that the group has a global distribution even though most of the species are restricted to intertidal habitats, has led to the hypothesis that dispersal and speciation within the group has been driven by the process of continental drift. However, this has never been confirmed empirically. With morphology and two molecular loci, COI and 18S, we calculated phylogenetic trees by analysing datasets separately and in combination using Maximum Parsimony, Maximum Likelihood and Bayesian Inference. Using different models of evolution in combination with different statistical approaches, we show that two major clade divergences were consistent with historic drifting of continents, suggesting that vicariance has played an important role for the speciation within the E. coulli-group. Furthermore, we found that reconstructions of past tectonic drifting since the Devonian (416–359 million years ago) were able to explain present species distributions, and suggest that the group originated in a supposedly vast shallow marine environment in north-eastern Gondwana by the mid-late Silurian, 426–416 million years ago.

中文翻译：

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Echinoderes coulli-group (Kinorhyncha : Cyclorhagida : Echinoderidae) 的系统发育——一个被困在潮间带的世界性物种组

Kinorhyncha 是在世界各地发现的微观底栖海洋无脊椎动物门，从北极到南极洲，从潮间带到深海。在物种最丰富的 Echinoderes 属中，我们发现了一个假定的单系物种群，即所谓的 Echinoderes coulli-group。E. coulli-group 物种的显着形态相似性以及该群体具有全球分布的事实，即使大多数物种仅限于潮间带栖息地，导致假设该群体内的扩散和物种形成是由大陆漂移的过程。然而，这从未得到经验证实。借助形态学和两个分子位点 COI 和 18S，我们通过使用最大简约法单独和组合分析数据集来计算系统发育树，最大似然和贝叶斯推理。使用不同的进化模型结合不同的统计方法，我们表明两个主要的进化枝分歧与大陆的历史漂移一致，这表明替代在 E. coulli 群内的物种形成中发挥了重要作用。此外，我们发现自泥盆纪（4.16-3.59 亿年前）以来的过去构造漂移的重建能够解释现在的物种分布，并表明该群体在中期起源于冈瓦纳东北部一个据称广阔的浅海海洋环境。 -晚志留纪，426-4.16 亿年前。我们表明，两个主要的进化枝分歧与大陆的历史漂移一致，表明替代在 E. coulli 群内的物种形成中发挥了重要作用。此外，我们发现自泥盆纪（4.16-3.59 亿年前）以来的过去构造漂移的重建能够解释现在的物种分布，并表明该群体在中期起源于冈瓦纳东北部一个据称广阔的浅海海洋环境。 -晚志留纪，426-4.16 亿年前。我们表明，两个主要的进化枝分歧与大陆的历史漂移一致，表明替代在 E. coulli 群内的物种形成中发挥了重要作用。此外，我们发现自泥盆纪（4.16-3.59 亿年前）以来的过去构造漂移的重建能够解释现在的物种分布，并表明该群体在中期起源于冈瓦纳东北部一个据称广阔的浅海海洋环境。 -晚志留纪，426-4.16 亿年前。