Molecular phylogenetic analyses of Riccia and Marchantiales. This dissertation consists of three main subproject manuscripts. In manuscript 1, preliminary molecular phylogenies of the Marchantiales are presented. Relative rate tests reveal significant heterogeneity in the nuclear LSU rDNA data. Monophyletic Aytoniaceae, Cleveaceae and Riccia are indicated.
Topologies imply that extant acarpocephalate taxa are derived from carpocephalate forms.
Monoclea positions well within Marchantiales sensu stricto. An unresolved marchantioid polytomy follows the well-supported basal nodes. This polytomy may correspond to an explosive radiation of taxa coincident with extreme conditions and ecological reorganizations of the Permo-Triassic. Unexpected placement of several taxa is well-supported, suggesting a propensity in Riccia for volatile morphology not reflected in the underlying genetic history. The complex thallus is envisioned to have originated from a transitional form with a highly regularized, bilaterally-symmetrical reticulum of fused dorsal lappets.