The branching pattern of major groups of land plants inferred from parsimony analysis of ribosomal RNA sequences |
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Authors: | S Barnabas S Krishnan J Barnabas |
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Institution: | (1) Division of Biochemical Sciences, National Chemical Laboratory, 411 008 Pune, India |
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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 andLophocolea appear to be phylogenetically close and together withPlagiomnium form a monophyletic group.Lycopodium andPsilotum 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 joiningCycas. Among the conifers,Metasequoia,Juniperus andTaxus emerge as a branch independent ofPinus 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.
Since deceased. |
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Keywords: | Phylogenetic analysis rRNA sequences branching pattern land plants age of angiosperms |
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