MOLECULAR EVOLUTION OF PTERIDOPHYTES AND THEIR RELATIONSHIP TO SEED PLANTS - EVIDENCE FROM COMPLETE 18S RIBOSOMAL-RNA GENE-SEQUENCES

Complete 18S ribosomal RNA sequence data from representatives of all e xtant pteridophyte lineages together with RNA sequences from different seed plants were used to infer a molecular phylogeny of vascular plan ts that included all major land plant lineages. The molecular data ind icate that lycopsids are monophyletic and are the earliest diverging g roup within the vascular land plants, whereas Psilotum nudum is more c losely related to the seed plants than to other pteridophyte lineages. The phylogenetic toes based on maximum likelihood, parsimony and dist ance analyses show substantial agreement with the evolutionary relatio nships of land plants as interpreted from the fossil record.