Division of Fish Genetics and Biotechnology, Central Institute of Fisheries Education, Versova, Andheri West, Mumbai, 400061, India,
Mol Biol Rep. 2014 Jan;41(1):447-57. doi: 10.1007/s11033-013-2879-6. Epub 2013 Nov 29.
The elasmobranchs (sharks, rays and skates) being the extant survivors of one of the earliest offshoots of the vertebrate evolutionary tree are good model organisms to study the primitive vertebrate conditions. They play a significant role in maintaining the ecological balance and have high economic value. Due to over-exploitation and illegal fishing worldwide, the elasmobranch stocks are being decimated at an alarming rate. Appropriate management measures are necessary for restoring depleted elasmobranch stocks. One approach for restoring stocks is implementation of conservation measures and these measures can be formulated effectively by knowing the evolutionary relationship among the elasmobranchs. In this study, a total of 30 species were chosen for molecular phylogeny studies using mitochondrial cytochrome c oxidase subunit I, 12S ribosomal RNA gene and nuclear Internal Transcribed Spacer 2. Among different genes, the combined dataset of COI and 12S rRNA resulted in a well resolved tree topology with significant bootstrap/posterior probabilities values. The results supported the reciprocal monophyly of sharks and batoids. Within Galeomorphii, Heterodontiformes (bullhead sharks) formed as a sister group to Lamniformes (mackerel sharks): Orectolobiformes (carpet sharks) and to Carcharhiniformes (ground sharks). Within batoids, the Myliobatiformes formed a monophyly group while Pristiformes (sawfishes) and Rhinobatiformes (guitar fishes) formed a sister group to all other batoids.
软骨鱼纲（鲨鱼、鳐鱼和魟鱼）是脊椎动物进化树最早的分支之一的现存幸存者，是研究原始脊椎动物状况的良好模式生物。它们在维持生态平衡方面发挥着重要作用，具有很高的经济价值。由于全球范围内的过度捕捞和非法捕捞，软骨鱼种群正以惊人的速度减少。为了恢复枯竭的软骨鱼种群，需要采取适当的管理措施。恢复种群的一种方法是实施保护措施，而通过了解软骨鱼之间的进化关系，可以有效地制定这些措施。在这项研究中，选择了 30 个物种进行分子系统发育研究，使用线粒体细胞色素 c 氧化酶亚基 I、12S 核糖体 RNA 基因和核内转录间隔区 2。在不同的基因中，COI 和 12S rRNA 的联合数据集产生了一个具有显著自举/后验概率值的良好解决的树拓扑结构。结果支持鲨鱼和鳐鱼的相互单系性。在 Galeomorphii 中，Heterodontiformes（牛鲨）形成了与 Lamniformes（鲭鲨）：Orectolobiformes（地毯鲨）和 Carcharhiniformes（地鲨）的姐妹群。在鳐鱼中，Myliobatiformes 形成了一个单系群，而 Pristiformes（锯鳐）和 Rhinobatiformes（吉他鱼）与所有其他鳐鱼形成了姐妹群。
