Molecular evolution of pteridophytes and their relationship to seed plants: Evidence from complete 18S rRNA gene sequences

Complete 18S ribosomal RNA sequence data from representatives of all extant pteridophyte lineages together with RNA sequences from different seed plants were used to infer a molecular phylogeny of vascular plants that included all major land plant lineages. The molecular data indicate that lycopsids are monophyletic and are the earliest diverging group within the vascular land plants, whereas Psilotum nudum is more closely related to the seed plants than to other pteridophyte lineages. The phylogenetic toes based on maximum likelihood, parsimony and distance analyses show substantial agreement with the evolutionary relationships of land plants as interpreted from the fossil record.