Osteology of the South Asian Genus Psilorhynchus McClelland, 1839 (Teleostei: Ostariophysi: Psilorhynchidae), with investigation of its phylogenetic relationships within the order Cypriniformes

Members of the genus Psilorhynchus are small benthic fishes, commonly referred to as torrent minnows, which inhabit the fast to swift flowing water bodies of the Indo‐Burma region and the Western Ghats of Peninsular India. Despite being described scientifically in the mid 18^th century, the morphology of Psilorhynchus remains poorly known and its phylogenetic placement within the order Cypriniformes is a matter of considerable debate. In this paper the osteology of Psilorhynchus sucatio is described and illustrated in detail. Notes and/or illustrations on the osteology of 12 other species of Psilorhynchus are also provided for the first time. A phylogenetic investigation of the position of Psilorhynchus within the order Cypriniformes is also conducted. Analysis of 127 morphological characters scored for 52 ingroup taxa (including 12 species of Psilorhynchus) and four outgroup taxa resulted in 14 equally parsimonious cladograms (287 steps long; consitency index, CI = 0.48; retention index, RI = 0.88). Psilorhynchus is recovered as the sister group to the family Cyprinidae, and is regarded as a member of the superfamily Cyprinoidea, which forms the sister group to the Cobitoidea (including all other cypriniform families). The sistergroup relationship between Psilorhynchus and Cyprinidae is supported by eight derived characters (five of which are homoplastic within the order Cypriniformes). The monophyly of Psilorhynchus is supported by 16 derived characters (eight of which are homoplastic within Cypriniformes). Three species groups of Psilorhynchus are proposed, the Psilorhynchus balitora group (including P. amplicephalus, P. balitora, P. breviminor, P. nepalensis, P. rahmani, P. pavimentatus, and P. brachyrhynchus), the Psilorhynchus gracilis group (including P. gracilis, P. melissa, P. robustus, and P. tenura), and the Psilorhynchus homaloptera group (including P. arunachalensis, P. homaloptera, P. microphthalmus, and P. pseudecheneis). The continued use of the family group name Psilorhynchidae is recommended. Comments on the interrelationships of the Cypriniformes are also provided. © 2011 The Linnean Society of London, Zoological Journal of the Linnean Society, 2011.     

斑纹薄鳅(Leptobotia zebra)应该为斑纹沙鳅(Sinibotia zebra)

斑纹薄鳅(Leptobotia zebra)最初是由Wu(1939)描述的一个新种,当时定名为斑纹沙鳅(Botia zebra),后来Chen(1980)根据眼下刺不分叉将其改归为薄鳅属的物种。本研究通过对线粒体DNA细胞色素b基因序列的测定和分析,发现斑纹薄鳅和薄鳅属(除斑纹薄鳅)物种间的平均遗传距离为0.177,和中华沙鳅属物种美丽沙鳅(Sinibotia pulcher)的平均遗传距离仅为0.057。系统发育分析发现斑纹薄鳅并未和薄鳅属的物种聚在一起,而是和中华沙鳅属物种美丽沙鳅聚在一起形成姐妹群。进一步对斑纹薄鳅进行形态学特征检视,发现该物种具有颊部裸露无鳞、颏部具一对纽状突起等中华沙鳅属鱼类的特征,但又具有眼下刺简单不分叉的薄鳅属鱼类的特征。结合分子数据分析的结果,将斑纹薄鳅订正为中华沙鳅属的物种,其命名为斑纹沙鳅(Sinibotia zebra)。另外,对沙鳅科鱼类属的划分标准及形态特征的演化也进行了讨论。     

Comparative analysis reveals that polyploidy does not decelerate diversification in fish

While the proliferation of the species‐rich teleost fish has been ascribed to an ancient genome duplication event at the base of this group, the broader impact of polyploidy on fish evolution and diversification remains poorly understood. Here, we investigate the association between polyploidy and diversification in several fish lineages: the sturgeons (Acipenseridae: Acipenseriformes), the botiid loaches (Botiidae: Cypriniformes), Cyprininae fishes (Cyprinidae: Cypriniformes) and the salmonids (Salmonidae: Salmoniformes). Using likelihood‐based evolutionary methodologies, we co‐estimate speciation and extinction rates associated with polyploid vs. diploid fish lineages. Family‐level analysis of Acipenseridae and Botiidae revealed no significant difference in diversification rates between polyploid and diploid relatives, while analysis of the subfamily Cyprininae revealed higher polyploid diversification. Additionally, order‐level analysis of the polyploid Salmoniformes and its diploid sister clade, the Esociformes, did not support a significantly different net diversification rate between the two groups. Taken together, our results suggest that polyploidy is generally not associated with decreased diversification in fish – a pattern that stands in contrast to that previously observed in plants. While there are notable differences in the time frame examined in the two studies, our results suggest that polyploidy is associated with different diversification patterns in these two major branches of the eukaryote tree of life.