A reassessment of the taxonomic position of Miehea Ochyra

The taxonomic position of Miehea Ochyra has remained questionable since the type species M. himalayana Ochyra was synonymized into Hylocomium indicum Dixon, which was either treated as Miehea in the Hylocomiaceae or as a Ptychodium of the Thuidiaceae. In this study I re-examine the Miehea taxa and synonymize them to Pseudopleuropus Tak. based on the ontogenetic sequence of paraphyllia as well as other morphological characters of gametophytes. Miehea indica appears distinct from M. himalayana by having asexual gemmae and caudate apex of stem-leaves. Three species in Pseudopleuropus are recognized, i.e., P. morrisonensis Nog., P. indicus (Dix.) comb. nov., and P. himalayanus (Ochyra) comb. nov. Miehea (=Pseudopleuropus) is catalogued in the Leskeaceae and excluded from the Hylocomiaceae or Thuidiaceae based on the leskeoid peristomes (vs. hypnoid ones) and the unbranched paraphyllia. Pseudopleuropus is related to Lescuraea in sharing several gametophytic characteristics: differentiation of stemand branch-leaves, concave leaves, and lanceolate laminal cells. The differentiation of dwarfness, an autapomorphy in P. morrisonensis, is suggested to be a key innovation for adapting to the selective regime switching from terrestrial to corticolous habitat.