Haplomitriaceae and Treubiaceae
These two families were never recognized as closely related until recent molecular analyses gave strong support of a sister group relationship. In a recent taxonomic treatment of the liverworts, the two groups were assigned to different orders within the simple thalloids. Nevertheless, the Haplomitriopsida, as this lineage is now known, do share several key features:
- Tetrahedral apical cells
- Stalked slime papillae
- Calyptra or perigynium without perichaetial scales
| Figure 4. Haplomitriopsida (based on the topology from the 5 partition Bayesian analysis of 5 loci including chloroplast, nuclear, and mitochondrial DNA). Numbers above the branches are Maximum Parsimony bootstrap values/homogeneous Bayesian posterior probabilities (PPs)/5-partition Bayesian PPs/14-partition Bayesian PPs. |
Figure 4 (Forrest et al., 2006) shows more detail of the relationships within this group. An expanded analyses of species in the Haplomitriopsida (Forrest et al., unpublished data), showed that there is more DNA nucleotide variability in this clade than in the rest of the hornwort division combined!
Haplomitrium blumei (photo by D. Long) |
Treubia lacunosa (photo by B. Crandall-Stotler) |
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