Takezaki Naoko, Nishihara Hidenori
Life Science Research Center, Kagawa University, Mikicho, Kitagun, Kagawa, Japan.
Department of Life Science and Technology, Tokyo Institute of Technology, Midori-ku, Yokohama, Kanagawa Japan.
Genome Biol Evol. 2017 Jan 1;9(1):93-101. doi: 10.1093/gbe/evw288.
In a previous analysis of the phylogenetic relationships of coelacanths, lungfishes and tetrapods, using cartilaginous fish (CF) as the outgroup, the sister relationship of lungfishes and tetrapods was constructed with high statistical support. However, using as the outgroup ray-finned fish (RF), which are more taxonomically closely related to the three lineages than CF, the sister relationship of coelacanths and tetrapods was most often constructed depending on the methods and the data sets, but the statistical support was generally low except in the cases in which the data set including a small number of species was analyzed. In this study, instead of the fast evolving ray-finned fish, teleost fish (TF), in the previous data sets, by using two slowly evolving RF, gar and bowfin, as the outgroup, we showed that the sister relationship of lungfishes and tetrapods was reconstructed with high statistical support. In our analysis the evolutionary rates of gar and bowfin were similar to each other and one third to one half of TF. The difference of the amino acid frequencies of the two species with other lineages was larger than those of TF. This study provides a strong support for lungfishes as the closest relative of tetrapods and indicates the importance of using an appropriate outgroup with small divergence in phylogenetic construction.
在先前一项对腔棘鱼、肺鱼和四足动物系统发育关系的分析中，以软骨鱼（CF）作为外类群，肺鱼和四足动物的姐妹关系在高统计支持下得以构建。然而，使用辐鳍鱼（RF）作为外类群，其在分类学上比CF与这三个谱系的关系更为密切，腔棘鱼和四足动物的姐妹关系大多根据方法和数据集构建，但除了分析包含少量物种的数据集的情况外，统计支持通常较低。在本研究中，我们没有使用先前数据集中快速进化的辐鳍鱼，而是使用两种进化缓慢的RF，雀鳝和弓鳍鱼，作为外类群，结果表明肺鱼和四足动物的姐妹关系在高统计支持下得以重建。在我们的分析中，雀鳝和弓鳍鱼的进化速率彼此相似，且为辐鳍鱼的三分之一到二分之一。这两个物种与其他谱系的氨基酸频率差异大于辐鳍鱼。本研究为肺鱼是四足动物的最亲近亲属提供了有力支持，并表明在系统发育构建中使用分歧小的合适外类群的重要性。
