PRELIMINARY INFERENCES OF THE PHYLOGENY OF BRYOPHYTES FROM NUCLEAR-ENCODED RIBOSOMAL-RNA SEQUENCES

Ribosomal RNA sequences and cladistic analysis were used to infer a phylogeny for eight bryophyte taxa. Portions of the cytoplasmic large (26S-like) and small (18S-like) subunit ribosomal RNA genes were sequenced for three marchantioid liverworts (Asterella, Conocephalum, and Riccia), three mosses (Atrichum, Fissidens, and Plagiomnium), and two hornworts (Phaeoceros and Notothylas). Cladistic analysis of these data suggests that the homworts are the sister group to the mosses, the mosses and hornworts form a clade that is sister to the tracheophytes, and the liverworts form a clade sister to the other land plants. These results differ from previous cladistic analyses based on morphology, ultrastructure, and biochemistry, wherein the mosses alone are sister group to the tracheophytes. We conclude that cladistic analysis of molecular data can provide an independent data set for the study of bryophyte phylogeny, but the differences between the molecular and morphological results are a topic for further investigation.