PHYLOGENETIC-RELATIONSHIPS OF BRYOPHYTES INFERRED FROM NUCLEAR-ENCODED RIBOSOMAL-RNA GENE-SEQUENCES

We investigate phylogenetic relationships among hornworts, liverworts and mosses, and their relationships to other green plant groups, by an alysis of nucleotide variation in complete 18s rRNA gene sequences of three green algae, two homworts, seven liverworts, nine mosses, and si x tracheophytes. Parsimony and maximum-likelihood analyses yield a sin gle optimal tree in which the hornworts are resolved as the basal grou p among land plants, and the liverworts and mosses are sister taxa tha t together form the sister clade to the tracheophytes. This phylogeny is internally robust as indicated by decay indices and by comparison ( using both parsimony and likelihood criteria) to topologies representi ng five alternative hypotheses of bryophyte relationships. We discuss some possible reasons for differences between the phylogeny inferred f rom the rRNA data and those inferred from other character sets.