Data from: At least some meiofaunal species are not everywhere. Indication of geographic, ecological and geological barriers affecting the dispersion of species of Ototyphlonemertes (Nemertea, Hoplonemertea)

Most meiofauna species are known to have a broad distribution with no apparent barriers to their dispersion. However, different morphological and/or molecular methods supported patterns of diversity and distribution that may be different among taxa while also conflicting within the same group. We accurately assessed the patterns of geographic distribution in actual genetic species of a marine meiofauna animal model: Ototyphlonemertes. Specimens were collected from several sites around Europe, Northern and Central America, Southern America, Pacific Islands and Asia. We sequenced regions of two mitochondrial and two nuclear genes. By using single-gene, concatenated dataset, and multi-locus approaches and different DNA-taxonomy methods we disentangled the actual diversity and the spatial structures of haplotypes tested the possible correlation between the genetic diversity and geographic distance, and the spatial structures of haplotypes. Results show (i) the importance of using several genes to uncover both diversity and highlight phylogeographic relationships among species, and that (ii) independent genetic evolutionary entities have a narrower distribution than morphological species. Moreover, (iii) the Mantel test supported a positive correlation between genetic and geographical distance. We also determined the divergence time between some of our entities sampled from the two sides of Panama Isthmus. Results suggest such entities have been separated for a period of time that coincides with the geological closure of the seaway across the Isthmus. We, therefore, propose that in addition to distance other geological and ecological conditions also are barriers to the dispersion and gene flow in marine meiofauna organisms.

众所周知，绝大多数小型底栖生物（meiofauna）物种拥有广泛的分布范围，不存在明显的扩散障碍。然而，不同的形态学与/或分子学方法所支持的多样性与分布模式，不仅在不同类群间存在差异，在同一类群内部也可能相互矛盾。

我们以海洋小型底栖生物模式物种Ototyphlonemertes为研究对象，准确评估了其实际遗传物种的地理分布模式。研究样本采自欧洲、北美洲与中美洲、南美洲、太平洋群岛及亚洲的多个采样位点。我们对两个线粒体基因与两个核基因的区域开展了测序。通过单基因、联合数据集以及多位点分析方法，并结合不同的DNA分类学（DNA-taxonomy）手段，我们厘清了实际物种多样性与单倍型的空间结构，检验了遗传多样性与地理距离之间的潜在相关性，同时分析了单倍型的空间结构。

研究结果显示：其一，需借助多个基因方能全面揭示物种多样性，并阐明物种间的系统地理关系；其二，独立的遗传进化实体较形态学物种拥有更狭窄的分布范围；其三，曼特尔检验（Mantel test）证实遗传距离与地理距离呈显著正相关。

此外，我们还测定了采自巴拿马地峡（Panama Isthmus）两侧的部分遗传实体的分化时间。结果表明，这些实体的分离时长与巴拿马地峡海峡地质闭合的时间高度吻合。因此我们提出，除地理距离外，其他地质与生态条件同样可构成海洋小型底栖生物扩散与基因流的障碍。