The branching pattern of major groups of land plants inferred from parsimony analysis of ribosomal RNA sequences.
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Date
1995-03
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Abstract
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 is
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 fem-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.
The phylogeny derived from the available ss-RNA sequences shows that angiosperms are
monophyletic with monocots and dicots diverging from a common stem. The nucleotide
replacements during angiosperm descent from the gymnosperm ancestor which presumably
arose around 370 my ago indicates that monocots and dicots diverged around 180 my ago,
which is compatible with the reported divergence estimate of around 200 my ago deduced
from chloroplast DNA sequences.
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Keywords
Phylogenetic analysis, rRNA sequences, branching pattern, land plants, age of angiosperms
Citation
Barnabas S, Krishnan S, Barnabas J. The branching pattern of major groups of land plants inferred from parsimony analysis of ribosomal RNA sequences. Journal of Biosciences. 1995 Mar; 20(2): 259-272.