Bryophyte phylogeny and the evolution of land plants: Evidence from development and ultrastrutcure

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Abstract
Phylogenetic analyses were carried out based on 132 ultrastructural, biochemical and developmental characters to develop a hypothesis for the principal lineages of extant land plants, in particular the relationships among and within hornworts, liverworts, and mosses. The organisms included five hornwort, 11 liverwort, eight moss, five lycophyte and three genera of spore-bearing vascular plants. Gametophytic features (65 characters) and sporophytic features (67 characters) were analyzed separately and together. The combined data set resulted in 26 most parsimonious (MP) trees (TL = 293) in which bryophytes were not monophyletic. Hornworts were the sister group to the remaining land plants, and mosses and liverworts were monophyletic, and formed the sister group to vascular plants. Hornworts showed a single arrangement with Megaceros as the apparent outgroup; however, decay analysis showed little support for this tree topology. MP trees for liverworts were variable in initial branch topologies, although most genera of Jungermanniales plus Metzgeriales formed a clade. Moss relationships were fully resolved, and Sphagnum was the outgroup to successive paraphyletic lineages for Takakia, Andreaea plus Andreaeobryum, Polytrichum, Tetraphis and the peristomate mosses. In trees one step longer, Takakia was the outgroup to the remaining genera. Relationships within vascular plants were poorly resolved, although Selaginella was the usual outgroup or it was part of larger lycophyte assemblages. These results suggest that there is extensive useful phylogenetic information at the base of the land plant clade in traditional morphogenetic combined with contemporary cytomorphogenetic approaches to systematic botany.

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