Armando Sánchez Juan, Lasker Howard R, Taylor Derek J
Department of Biological Sciences, 109 Cooke Hall, University at Buffalo (The State University of New York), Buffalo, NY 14260, USA.
Mol Phylogenet Evol. 2003 Oct;29(1):31-42. doi: 10.1016/s1055-7903(03)00090-3.
Gorgonian octocorals lack corroborated hypotheses of phylogeny. This study reconstructs genealogical relationships among some octocoral species based on published DNA sequences from the large ribosomal subunit of the mitochondrial RNA (lsu-rRNA, 16S: 524bp and 21 species) and the small subunit of the nuclear RNA (ssu-rRNA, 18S: 1815bp and 13 spp) using information from insertions-deletions (INDELS) and the predicted secondary structure of the lsu-rRNA (16S). There were seven short (3-10bp) INDELS in the 18S with consistent phylogenetic information. The INDELS in the 16S corresponded to informative signature sequences homologous to the G13 helix found in Escherichia coli. We found two main groups of gorgonian octocorals using a maximum parsimony analysis of the two genes. One group corresponds to deep-water taxa including species from the suborders Calcaxonia and Scleraxonia characterized by an enlargement of the G13 helix. The second group has species from Alcyoniina, Holaxonia and again Scleraxonia characterized by insertions in the 18S. Gorgonian corals, branching colonies with a gorgonin-containing flexible multilayered axis (Holaxonia and Calcaxonia), do not form a monophyletic group. These corroborated results from maternally inherited (16S) and biparentally inherited (18S) genes support a hypothesis of independent evolution of branching in the two octocoral clades.
柳珊瑚八放珊瑚缺乏经过证实的系统发育假说。本研究基于已发表的线粒体RNA大核糖体亚基（lsu - rRNA，16S：524bp，共21个物种）和核RNA小亚基（ssu - rRNA，18S：1815bp，共13个物种）的DNA序列，利用插入缺失（INDELS）信息和lsu - rRNA（16S）的预测二级结构，重建了一些八放珊瑚物种之间的谱系关系。18S中有7个短（3 - 10bp）的插入缺失，具有一致的系统发育信息。16S中的插入缺失对应于与大肠杆菌中发现的G13螺旋同源的信息性特征序列。通过对这两个基因进行最大简约分析，我们发现了柳珊瑚八放珊瑚的两个主要类群。一个类群对应深水分类单元，包括来自钙质亚目和硬骨亚目的物种，其特征是G13螺旋增大。第二个类群有来自海鸡冠亚目、全轴亚目以及再次出现的硬骨亚目的物种，其特征是18S中有插入。柳珊瑚，具有含柳珊瑚素的灵活多层轴的分支群体（全轴亚目和钙质亚目），并不形成一个单系类群。这些来自母系遗传（16S）和双亲遗传（18S）基因的证实结果支持了两个八放珊瑚分支独立进化的假说。
