López J Andrés, Ryburn Julie A, Fedrigo Olivier, Naylor Gavin J P
Florida Museum of Natural History, University of Florida, Gainesville, FL 32611, USA.
Mol Phylogenet Evol. 2006 Jul;40(1):50-60. doi: 10.1016/j.ympev.2006.02.011. Epub 2006 Mar 27.
We present a study of inter- and intra-familial relationships of the carcharhiniform shark family Triakidae aimed at testing existing hypotheses of relationships for this group and at improving understanding of the evolution of reproductive traits in elasmobranchs. Our analyses and conclusions are based on evidence from DNA sequences of four protein-coding genes (three from the mitochondrial genome and a single copy nuclear gene) from eight of the nine genera and 20 of the 39 species currently assigned to the Triakidae. The sequence data offer strong support for the following previously proposed triakid clades: Galeorhinini (Hypogaleus+Galeorhinus); a subset of the Iagini (Furgaleus+Hemitriakis but not Iago); and part of the Triakinae (Mustelus, Scylliogaleus and part of Triakis). Interestingly, the molecular data provide considerable evidence of paraphyly of the genera Triakis and Mustelus. Our results suggest that the subgenera Triakis and Cazon of Triakis represent two distinct lineages that are only distantly related and that the genus Mustelus as currently defined does not constitute a monophyletic assemblage unless S. quecketti and some species of Triakis (subgenus Cazon) are included in Mustelus. Within our sample of species of Mustelus (including Cazon and Scylliogaleus), the sequence data support two well-defined clades that can be diagnosed by mode of reproduction (placental vs. aplacental species). The phylogenetic framework presented here is used to infer key events in the evolution and loss of placental viviparity among carcharhiniform sharks.
我们对真鲨科鲨鱼的科内和科间关系进行了一项研究，旨在检验该类群现有关系假说，并增进对软骨鱼类生殖特征进化的理解。我们的分析和结论基于来自9个属中的8个属以及目前归入真鲨科的39个物种中的20个物种的4个蛋白质编码基因（3个来自线粒体基因组，1个单拷贝核基因）的DNA序列证据。序列数据为以下先前提出的真鲨科分支提供了有力支持：猫鲨亚科（Hypogaleus + Galeorhinus）；伊氏鲨亚科的一个子集（Furgaleus + Hemitriakis，但不包括伊氏鲨属）；以及三齿鲨亚科的一部分（鼬鲨属、锯鲨属和三齿鲨属的一部分）。有趣的是，分子数据提供了大量证据表明三齿鲨属和鼬鲨属是并系群。我们的结果表明，三齿鲨属的三齿鲨亚属和卡宗亚属代表两个截然不同且亲缘关系甚远的谱系，并且目前定义的鼬鲨属并不构成一个单系类群，除非将奎氏锯鲨和三齿鲨属（卡宗亚属）的一些物种纳入鼬鲨属。在我们所研究的鼬鲨属物种样本中（包括卡宗亚属和锯鲨属），序列数据支持两个界限分明的分支，可通过生殖方式（胎盘生殖与非胎盘生殖物种）来区分。这里呈现的系统发育框架用于推断真鲨科鲨鱼胎盘胎生的进化和消失过程中的关键事件。
