Department of Biology, University of Puerto Rico - Rio Piedras (UPRRP), San Juan, PR 00931-3360, PR, USA.
Mol Phylogenet Evol. 2011 Feb;58(2):207-17. doi: 10.1016/j.ympev.2010.11.018. Epub 2010 Nov 30.
Sharks are a diverse and ecologically important group, including some of the ocean's largest predatory animals. Sharks are also commercially important, with many species suffering overexploitation and facing extinction. However, despite a long evolutionary history, commercial, and conservation importance, phylogenetic relationships within the sharks are poorly understood. To date, most studies have either focused on smaller clades within sharks, or sampled taxa sparsely across the group. A more detailed species-level phylogeny will offer further insights into shark taxonomy, provide a tool for comparative analyses, as well as facilitating phylogenetic estimates of conservation priorities. We used four mitochondrial and one nuclear gene to investigate the phylogenetic relationships of 229 species (all eight Orders and 31 families) of sharks, more than quadrupling the number of taxon sampled in any prior study. The resulting Bayesian phylogenetic hypothesis agrees with prior studies on the major relationships of the sharks phylogeny; however, on those relationships that have proven more controversial, it differs in several aspects from the most recent molecular studies. The phylogeny supports the division of sharks into two major groups, the Galeomorphii and Squalimorphii, rejecting the hypnosqualean hypothesis that places batoids within sharks. Within the squalimorphs the orders Hexanchiformes, Squatiniformes, Squaliformes, and Pristiophoriformes are broadly monophyletic, with minor exceptions apparently due to missing data. Similarly, within Galeomorphs, the orders Heterodontiformes, Lamniformes, Carcharhiniformes, and Orectolobiformes are broadly monophyletic, with a couple of species 'misplaced'. In contrast, many of the currently recognized shark families are not monophyletic according to our results. Our phylogeny offers some of the first clarification of the relationships among families of the order Squaliformes, a group that has thus far received relatively little phylogenetic attention. Our results suggest that the genus Echinorhinus is not a squaliform, but rather related to the saw sharks, a hypothesis that might be supported by both groups sharing 'spiny' snouts. In sum, our results offer the most detailed species-level phylogeny of sharks to date and a tool for comparative analyses.
鲨鱼是一个多样化且具有重要生态意义的群体，包括一些海洋中最大的掠食性动物。鲨鱼在商业上也很重要，许多物种都遭受过度开发，面临灭绝的威胁。然而，尽管它们有着漫长的进化历史、商业价值和保护意义，但鲨鱼内部的系统发育关系仍未被充分了解。迄今为止，大多数研究要么集中在鲨鱼的较小分支上，要么在整个群体中稀疏地采样分类单元。更详细的种系发生关系将进一步深入了解鲨鱼的分类学，为比较分析提供工具，并有助于确定保护优先事项的系统发育估计。我们使用了四个线粒体和一个核基因来研究 229 种鲨鱼（包括所有八个目和 31 个科）的系统发育关系，这比以往任何研究中采样的分类单元数量都增加了四倍多。贝叶斯系统发育假说与先前关于鲨鱼系统发育的主要关系的研究一致；然而，在那些已经证明更具争议性的关系上，它在几个方面与最近的分子研究不同。该系统发育支持将鲨鱼分为两个主要群体，即 Galeomorphii 和 Squalimorphii，拒绝将 batoids 归入鲨鱼的 hypnosqualean 假说。在 Squalimorphii 中，Hexanchiformes、Squatiniformes、Squaliformes 和 Pristiophoriformes 目广泛是单系的，只有少数例外显然是由于数据缺失。同样，在 Galeomorphs 中，Heterodontiformes、Lamniformes、Carcharhiniformes 和 Orectolobiformes 目也广泛是单系的，只有少数几个物种“错位”。相比之下，根据我们的结果，许多目前公认的鲨鱼科并不是单系的。我们的系统发育关系为以前受到相对较少系统发育关注的 Squatiniformes 目各科之间的关系提供了一些首次澄清。我们的结果表明，Echinorhinus 属不是 squaliform，而是与锯鲨有关，这一假说可能得到这两个群体都具有“多刺”口鼻部的支持。总之，我们的结果提供了迄今为止最详细的鲨鱼种系发生关系，并为比较分析提供了工具。
