A molecular phylogeny of bryophytes based on nucleotide sequences of the mitochondrial nad5 gene

In contrast to animals, the slowly evolving mitochondrial nucleotide sequen ces of plants appear well suited to investigate phylogenetic relations betw een old taxonomic groups. Analysis of nad5 gene sequences in 47 bryophytes, the living representatives of very early land plants, confirm this assessm ent. Statistically reliable phylogenetic trees are obtained with different mathematical approaches. A group I intron sequence conserved in the nad5 ge ne of all 30 mosses and 15 liverworts investigated supports a sister group relationship of the two classes. The intron sequence adds phylogenetic info rmation for fine resolution on top of the conserved exon sequences down to the level of classically defined orders or families, respectively. This int ron is not present in the hornworts Anthoceros husnotii and A. punctatus. T he results allow statements on diverging taxonomic interpretations and supp ort the monophyly of the liverworts, mosses, Jungermanniidae, Marchantiidae and Bryidae, and allow recognition of subclasses like Hypnanae and Dicrana nae. Among the mosses, the derived orders (subclass Bryidae) are confidentl y set apart from the Sphagnales, Andreaeales, Polytrichales and Tetraphidal es with Buxbaumiales occupying a mediating position. Among the liverworts, full support is found for the classic separation of simple (jungermanniid) and complex thalloid (marchantiid) species with a strikingly low mitochondr ial sequence divergence among the latter.