Gouy M, Li W H
Center for Demographic and Population Genetics, University of Texas, Houston 77225.
Nature. 1989 May 11;339(6220):145-7. doi: 10.1038/339145a0.
How many primary lineages of life exist and what are their evolutionary relationships? These are fundamental but highly controversial issues. Woese and co-workers propose that archaebacteria, eubacteria and eukaryotes are the three primary lines of descent and their relationships can be represented by Fig. 1a (the 'archaebacterial tree') if one neglects the root of the tree. In contrast, Lake claims that archaebacteria are paraphyletic, and he groups eocytes (extremely thermophilic, sulphur-dependent bacteria) with eukaryotes, and halobacteria with eubacteria (the 'eocyte tree', Fig. 1b). Lake's view has gained considerable support as a result of an analysis of small subunit ribosomal RNA sequence data by a new approach, the evolutionary parsimony method. Here we report that analysis of small subunit data by the neighbour-joining and maximum parasimony methods favours the archaebacterial tree and that computer simulations using either the archaebacterial or the eocyte tree as a model tree show that the probability of recovering the model tree is very high (greater than 90 per cent) for both the neighbour-joining and maximum parsimony methods but is relatively low for the evolutionary parsimony method. Moreover, analysis of large subunit rRNA sequences by all three methods strongly favours the archaebacterial tree.
生命存在多少主要谱系，它们的进化关系是怎样的？这些都是基本但极具争议的问题。沃斯及其同事提出古细菌、真细菌和真核生物是三个主要的谱系，如果忽略谱系树的根部，它们的关系可用图1a表示（“古细菌树”）。相比之下，莱克认为古细菌是并系的，他将曙细菌（极端嗜热、依赖硫的细菌）与真核生物归为一类，而将嗜盐细菌与真细菌归为一类（“曙细菌树”，图1b）。由于采用一种新方法——进化简约法对小亚基核糖体RNA序列数据进行了分析，莱克的观点得到了相当多的支持。在此我们报告，用邻接法和最大简约法对小亚基数据进行分析支持古细菌树，并且以古细菌树或曙细菌树作为模型树进行计算机模拟表明，对于邻接法和最大简约法而言，恢复模型树的概率非常高（大于90%），但对于进化简约法来说则相对较低。此外，用这三种方法对大亚基rRNA序列进行分析都强烈支持古细菌树。
