Inferring Relationships of Early Land Plants Using 1KP Data

To understand the origin and evolution of critical adaptations in land plants, such as the embryo and vascular tissue, a robust hypothesis of relationships is required. While molecular systematics has resolved a number of enigmatic relationships among land plants, other relationships remain weakly resolved. Among these, the branching order of the three bryophyte lineages (mosses, liverworts, hornworts) has been particularly unstable, with multiple, conflicting topologies being recovered over the past two decades. It can be problematic to infer a phylogeny using molecular data at this time scale; the earlier bryophyte lineage diverged from the remaining land plants over 450 million years ago. However, genome-scale data is able to provide a significantly larger set of characters that may be informative for such analyses. A well resolved phylogeny resulting from the analysis of 852 nuclear genes, as part of the 1KP project, suggests that mosses and liverworts comprise a clade, which is inconsistent with the widely accepted view that bryophytes form a paraphyletic grade at the base of land plants. Using this topology, we are now testing hypotheses of gene and gene family evolution in bryophytes. The analyses presented here are focused on inferring the origin and diversification of horizontally acquired fungal genes in early land plants, and on the reconstruction of gene family expansions and contractions in bryophytes.