Data from: Multiple independent colonizations into the Congo Basin during the continental radiation of African Mastacembelus spiny eels

Aim: There has been recent interest in the origin and assembly of continental biotas based on densely sampled species-level clades, however, studies from African freshwaters are few so that the commonality of macroevolutionary patterns and processes among continental clades remain to be tested. Within the Afrotropics, the Congo Basin contains the highest diversity of riverine fishes, yet it is unclear how this fauna was assembled. To address this, and the diversification dynamics of a continental radiation, we focus on African Mastacembelus spiny eels. Location: Afrotropical freshwaters. Methods: The most complete molecular phylogeny to date was reconstructed for African spiny eels. Divergence times were estimated applying a Bayesian relaxed clock comparing fossil and geological calibrations across nuclear and mitochondrial trees. Biogeographic reconstructions, applying a dispersal–extinction–cladogenesis model and lineage diversification dynamics were examined. Results: Spiny eels originated in Asia and colonized Africa c. 15.4 Ma (95% HPD: 23.9–8.8 Ma) from which their subsequent radiation across the Afrotropics was best fitted by a constant rate model. Ancestral state estimation identified multiple colonization events into the Congo Basin, whereas all other regions were likely to have been colonized once indicating considerable geographic constraints. Application of the fossil calibration gave similar age estimates across datasets, whereas a geological calibration estimated considerably older nuclear divergences. Main conclusions: Despite profound environmental events during the evolutionary history of the group, there is no evidence for rapid lineage diversification. This finding supports several recent studies on tropical continental radiations that contrast to the common pattern of density-dependent diversification. We further show that dispersal has occurred into, as well as out of the Congo Basin, indicating the importance of this region in the generation of biodiversity.研究目标：当前学界基于密集采样的物种级支系，对大陆生物群的起源与组装机制愈发关注，但针对非洲淡水生态系统的相关研究仍较为匮乏，导致大陆支系间宏观进化模式与过程的共性仍有待验证。在非洲热带区中，刚果盆地（Congo Basin）拥有最为丰富的河流鱼类多样性，但该区域鱼类区系的组装过程尚不明确。为解决这一问题，并解析大陆辐射演化类群的分化动态，本研究聚焦于非洲刺鳅属（Mastacembelus）刺鳗。 研究区域：非洲热带淡水水域。 研究方法：本研究重建了迄今最完整的非洲刺鳗分子系统发育树。通过贝叶斯宽松分子钟（Bayesian relaxed clock），结合核基因与线粒体基因树的化石校准及地质校准方案，估算了类群的分化时间。同时采用扩散-灭绝-成分支模型（dispersal–extinction–cladogenesis model）进行生物地理重建，并分析了支系分化动态。 研究结果：刺鳗起源于亚洲，于约1540万年前（95%最高后验密度区间HPD：23.9~8.8 Ma）扩散至非洲；后续在非洲热带区的辐射演化最符合恒定速率模型。祖先状态重建结果显示，刚果盆地存在多次殖民事件，而其余区域均仅出现过一次殖民事件，表明存在较强的地理约束。基于化石校准的分化时间估算结果在不同数据集间较为一致，而地质校准则估算出更为古老的核基因分化时间。 主要结论：尽管该类群的演化历史中伴随有剧烈的环境事件，但并未发现支系快速分化的证据。这一结果支持了多项针对热带大陆辐射演化类群的近期研究，与常见的密度制约型分化模式形成鲜明对比。本研究进一步证实，既有向刚果盆地的扩散，也有从刚果盆地向外的扩散，表明该区域在生物多样性产生过程中具有重要意义。