Origins of the tripartite world

The numbers of additional steps (S) required to force molecules into monophyly were calculated based on class (class I and II tRNAs) and organismal (three superkingdoms of life or viruses) constraints using MP analyses of combined tRNA structure and sequence data. The length of the most parsimonious trees derived from the combined data set was 10,083 steps. Each constrained group is given in parentheses and groups of tRNA molecules are indicated by superkingdoms of life (Archaea, Bacteria, and Eukarya) or viruses. Both chloroplast and mitochondria tRNAs were included in Bacteria. A = Archaea, B = Bacteria, E = Eukarya, V = viruses. CH, competing hypothesis; H, non-competing hypothesis.

基于类群（I类和II类转运RNA（transfer RNA, tRNA））与生物类群（生命的三个超界或病毒）的约束条件，结合转运RNA（tRNA）结构与序列数据的最大简约法（Maximum Parsimony, MP）分析，计算了将分子强制为单系群所需的额外步数（S）。由该联合数据集得到的最大简约树总步数为10083步。每个约束组以括号标注，转运RNA分子类群则以生命超界（古菌域（Archaea）、细菌域（Bacteria）、真核生物域（Eukarya））或病毒进行标识。细菌域类群同时包含叶绿体与线粒体来源的转运RNA。A代表古菌域，B代表细菌域，E代表真核生物域，V代表病毒。CH代表竞争性假说，H代表非竞争性假说。