THE BRANCHING PATTERN OF MAJOR GROUPS OF LAND PLANTS INFERRED FROM PARSIMONY ANALYSIS OF RIBOSOMAL RNA SEQUENCES

摘要

The parsimony and bootstrap branching pattern of major groups of land plants derived from relevant 5S rRNA sequence trees have been discussed in the light of paleobotanical and morphological evidences. Although 5S rRNA sequence information a not useful for dileneating angiosperm relationships, it does capture the earlier phase of land plant evolution. The consensus branching pattern indicates an ancient split of bryophytes and vascular plants from the charophycean algal stem. Among the bryophytes, Marchantia and Lophocolea appear to be phylogenetically close and together with Plagiomnium form a monophyletic group. Lycopodium and Psilotum arose early in vascular land plant evolution, independent of fern-sphenopsid branch. Gymnosperms are polyphyletic; conifers, Gnetales and cycads emerge in that order with ginkgo joining Cycas. Among the conifers, Metasequoia, Juniperus and Taxus emerge as a branch independent of Pinus which joins Gnetales.