ABSTRACT

A comparison of Jungermanniidae and Marchantiidae as subclasses of the Hepaticopsida reveals problems with respect to the phylogenetic relations between both groups. This chapter presents a molecular approach by sequencing the complete 18S rRNA gene of 40 bryophyte species to obtain numerical data. The systematic classification of bryophytes has been based on morphological, anatomical, ontogenetic, biochemical, and developmental characters, and on the values assigned by taxonomists to these characters. The evolutionary trees based on molecular data have been compared with several morphological and biochemical characters used in classical taxonomy. In contrast to the traditional view of bryophyte taxonomy, the analysis of the extant bryophytes yields in all trees two sister groups that are not identical with the classification of liverworts and mosses. One group comprises only the Marchantiopsida, whereas the second comprises all other bryophyte species tested of the two classes Jungermanniopsida and Bryopsida.