The South and South‐East Asian freshwater fish genus Systomus (Cyprinidae) comprises 17 valid species. Six nominal species, including three endemics, have been reported from Sri Lanka, a continental island separated from India by a shallow‐shelf sea. The species diversity of Systomus on the island has until now not been assessed; neither has an evaluation been made of their phylogenetic history. Here, based on an analysis of the nuclear recombination activating protein 1 (rag1), and mitochondrial cytochrome c oxidase subunit 1 (cox1) and cytochrome b (cytb) gene markers, and a morphological examination of 143 specimens from 49 locations in Sri Lanka, we reassess the diversity of Systomus on the island and analyse patterns of their evolution and biogeography. Divergence‐time estimates, based on a substitution rate calibration, date the basal split between Systomus and its sister group, the Afrotropical small barbs, to 30.0 Ma (95% highest posterior density: 25.4–35.2 Ma). The species of Systomus belong to two distinct clades. The first includes the Sri Lankan endemics S. asoka, S. martenstyni and S. pleurotaenia, which comprise an insular diversification following the immigration of a common ancestor during the Oligocene. The second, which includes the remaining species of Indian, Sri Lankan and South‐East Asian Systomus, has a crown age dating to the Late Miocene. Morphological and molecular species delimitation analyses failed to validate the two nominal species, S. spilurus and S. timbiri, previously reported from Sri Lanka: both are considered synonyms of S. sarana, as are the nomina S. chryseus, S. chrysopoma, S. laticeps, S. rufus, S. pinnauratus and S. subnasutus. Four genetically and geographically discrete lineages of S. sarana occur in the island, and three in India. Molecular species delimitation analysis suggests these all belong to a single species, S. sarana. The genetically distinct Sri Lankan populations of S. sarana result from Plio‐Pleistocene dispersal or vicariance events between India and Sri Lanka—as a result of emergence and inundation of the now submerged isthmus connecting the two landmasses—as well as autochthonous insular diversification.

中文翻译：

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斯里兰卡 Systomus (Teleostei, Cyprinidae) 的多样性、系统发育和生物地理学

南亚和东南亚淡水鱼属 Systomus (Cyprinidae) 包括 17 个有效物种。据报道，斯里兰卡是一个大陆岛屿，与印度被浅海隔开，有六个名义物种，包括三个地方性物种。岛上的 Systomus 物种多样性至今尚未得到评估；也没有对它们的系统发育历史进行评估。在此，基于对核重组激活蛋白 1 (rag1)、线粒体细胞色素 c 氧化酶亚基 1 (cox1) 和细胞色素 b (cytb) 基因标记的分析，以及对斯里兰卡 49 个地点的 143 个标本的形态学检查，我们重新评估了岛上 Systomus 的多样性，并分析了它们的进化模式和生物地理学。基于替代率校准的发散时间估计，将 Systomus 及其姊妹组 Afrotropical small barbs 之间的基础分裂日期定为 30.0 Ma（95% 的最高后密度：25.4-35.2 Ma）。Systomus 的物种属于两个不同的进化枝。第一个包括斯里兰卡特有的 S. asoka、S. martenstyni 和 S. pleurotaenia，它们包括渐新世期间共同祖先移民后的岛屿多样化。第二种，包括印度、斯里兰卡和东南亚 Systomus 的其余物种，其冠龄可追溯到晚中新世。形态学和分子物种定界分析未能验证之前从斯里兰卡报道的两个名义物种 S. spilurus 和 S. timbiri：两者都被认为是 S. sarana 的同义词，S. chryseus、S. chrysopoma、S . laticeps、S. rufus、S. pinnauratus 和 S. 鼻下。S. sarana 的四个遗传和地理上离散的谱系出现在岛上，三个在印度。分子物种定界分析表明这些都属于单一物种 S. sarana。斯里兰卡 S. sarana 种群在遗传上不同是由印度和斯里兰卡之间的上新世-更新世扩散或替代事件造成的——这是连接两个大陆的现在淹没地峡的出现和淹没的结果——以及本土的岛屿多样化。