Morphology, molecules, and the phylogenetics of cetaceans

Recent phylogenetic analyses of cetacean relationships based on DNA sequence data have challenged the traditional view that baleen whales (Mysticeti) and toothed whales (Odontoceti) are each monophyletic, arguing instead that baleen whales are the sister group of the odontocete family Physeteridae (sperm whales). We reexamined this issue in light of a morphological data set composed of 207 characters and molecular data sets of published 12S, 16S, and cytochrome b mitochondrial DNA sequences. We reach four primary conclusions: (1) Our morphological data set strongly supports the traditional view of odontocete monophyly; (2) the unrooted molecular and morphological trees are very similar, and most of the conflict results from alternative rooting positions; (3) the rooting position of the molecular tree is sensitive to choice of artiodactyl outgroup taxa and the treatment of two small but ambiguously aligned regions of the 12S and 16S sequences, whereas the morphological root is strongly ...近期基于DNA序列数据开展的鲸类（Cetacea）系统发育关系分析，对“须鲸类（Mysticeti）与齿鲸类（Odontoceti）均为单系群”的传统观点提出了挑战，转而提出须鲸类是齿鲸类抹香鲸科（Physeteridae，抹香鲸）的姊妹群。本研究依托包含207个性状的形态学数据集，以及已发表的12S、16S及细胞色素b（cytochrome b）线粒体DNA（mitochondrial DNA）序列分子数据集，对该问题进行了重新检验。本研究得出四项核心结论：(1) 本研究的形态学数据集强力支持齿鲸类为单系群的传统观点；(2) 无根分子树与形态学树的拓扑结构高度相似，绝大多数冲突源于不同的根位置选择；(3) 分子树的根位置对偶蹄类外类群的选择，以及12S和16S序列中两个短小但比对模糊的区域的处理方式较为敏感，而形态学树的根则具有较强的……