Evolutionary Ecology and Systematics Lab, Department of Molecular Biology and Biotechnology, University of Peradeniya, Peradeniya, Sri Lanka; Postgraduate Institute of Science, University of Peradeniya, Peradeniya, Sri Lanka.
Ichthyology Section, Australian Museum, 6 College Street, Sydney, NSW 2010, Australia.
Mol Phylogenet Evol. 2020 Aug;149:106853. doi: 10.1016/j.ympev.2020.106853. Epub 2020 May 15.
The small, colourful freshwater fishes of the cyprinid genus Devario are among the many vertebrate groups that appear to have diversified on Sri Lanka, a continental Indian Ocean island, which is part of the Western Ghats-Sri Lanka Biodiversity Hotspot. Despite Sri Lanka having been connected with India via a wide isthmus intermittently until the Plio-Pleistocene and almost continuously since then, during sea-level low-stands, the number of species of Devario on Sri Lanka is comparable with that on the Indian Peninsula, some 25 times its size. Here, from a sampling of 27 Devario populations across Sri Lanka's major river basins and climatic zones, we present and analyze a phylogeny based on mitochondrial and nuclear DNA data. We show that five species of Devario occur on the island, all but one of which are endemic: Devario malabaricus is widespread throughout the lowlands and parts of central hills of Sri Lanka and southern India. A new narrow-range endemic, here described as D. memorialis sp. nov., was discovered in a remnant rainforest habitat at Aranayake (Ma Oya basin) in this study. It is immediately distinguished from Sri Lankan congeners by having only 8 (vs 9-12) branched dorsal-fin rays and by uncorrected pairwise genetic distances of more than 4.0% and 7.8% for cytochrome c oxidase subunit 1 and cytochrome b, respectively. Our results provide strong support for the monophyly of the entire Sri Lankan diversification of Devario. Divergence-timing analysis suggests the common ancestor dispersed to the island in the late Miocene, with the insular diversification in the island's south-western wet zone taking place during the Plio-pleistocene. There are signs of gene flow between the Indian and Sri Lankan populations of D. malabaricus until the late Pleistocene. Phylogenetic and haplotype-network analyses suggest basin-centric phylogeographic structure within the endemic species; D. malabaricus, however, shows little such structure in the island. Molecular and morphological analyses failed to identify D. annnataliae and D. udenii confidently as distinct species: they are considered synonyms of D. micronema. The morphological variation observed within D. micronema is likely attributable to polymorphism. The discordance between the mitochondrial and nuclear phylogenies for some samples of Devario in the present study suggest signs of mitochondrial introgression.
小型多彩淡水鱼类的 Cyprinid 属 Devario 是许多脊椎动物群体之一，这些群体似乎在斯里兰卡多样化，斯里兰卡是一个印度洋岛屿，是西高止山脉-斯里兰卡生物多样性热点地区的一部分。尽管斯里兰卡在上新世-更新世期间通过一个宽阔的地峡间歇性地与印度相连，并且自那时以来几乎一直相连，但在海平面低水位期间，斯里兰卡的 Devario 物种数量与印度半岛相当，尽管印度半岛的面积是斯里兰卡的 25 倍。在这里，我们从斯里兰卡主要河流流域和气候带的 27 个 Devario 种群中进行采样，提出并分析了基于线粒体和核 DNA 数据的系统发育。我们表明，岛上有五种 Devario 物种，除一种外均为特有种：Devario malabaricus 广泛分布于斯里兰卡低地和中部丘陵地区以及印度南部。本研究在阿兰亚克（Ma Oya 流域）的残余雨林栖息地中发现了一种新的狭窄范围特有种，这里将其描述为 D. memorialis sp. nov.。它与斯里兰卡的同种鱼类的区别在于仅具有 8 个（而不是 9-12 个）分支背鳍射线，并且未校正的成对遗传距离分别为细胞色素 c 氧化酶亚基 1 和细胞色素 b 的 4.0%以上和 7.8%以上。我们的结果为整个斯里兰卡 Devario 多样化的单系性提供了强有力的支持。分歧时间分析表明，共同祖先在中新世晚期分散到该岛，岛屿西南部湿润区的岛屿多样化发生在更新世。直到更新世晚期，印度和斯里兰卡的 D. malabaricus 种群之间仍有基因流动的迹象。系统发育和单倍型网络分析表明，在特有种中存在以流域为中心的地理结构；然而，D. malabaricus 在该岛几乎没有这种结构。分子和形态分析未能将 D. annnataliae 和 D. udenii 明确鉴定为不同的物种：它们被认为是 D. micronema 的同义词。在本研究中，一些 Devario 样本的线粒体和核系统发育之间的不匹配表明存在线粒体基因渗入的迹象。
