Molecular relationship of Treubia Goebel (Treubiaceae, Treubiopsida) and high taxonomic level classification of the Hepaticophytina - Studies in austral temperate rain forest bryophytes 6

The systematic position of Treubia, a liverwort genus commonly regarded as a basal member of the thallose Metzgeriidae (Jungermanniopsida), is evaluat ed on a molecular level by comparison of partial trnL(UAA) intron sequences of two specimens of Treubia from New Zealand (Treubia lacunosa, T. spec.), 21 other bryophytes (5 of Bryopsida, 7 of Marchantiopsida and 9 of Jungerm anniopsida), two eusporangiate ferns and Chlorella spec. Sequence compariso n reveals that the Treubia sequences share parsimony informative sites with the other liverworts, but also contain characteristic substitutions not pr esent in the sequences of both Marchantiopsida and Jungermanniopsida or eve n in all other bryophytes. In maximum parsimony and maximum likelihood tree s, the liverworts appear as monophyletic and thus constitute the subdivisio n Hepaticophytina of Bryophyta. Treubia does not cluster with either Marcha ntiopsida or Jungermanniopsida taxa. To express its isolated systematic pos ition, the new class Treubiopsida is proposed, with the Hepaticophytina now divided into three classes, Marchantiopsida, Jungermanniopsida and Treubio psida. A basal phylogenetic position of the Treubiopsida within liverworts is not indicated by the trnL(UAA) intron data, although the extant species of Treu bia and Apotreubia may be regarded as the most archaic living fossils in li verworts and extant models of an extinct plant group based on morphological characters.