Sciaromiopsis sinensis (Amblystegiaceae), revised to a member of Brachythecium (Brachytheciaceae)

Abstract. Sciaromiopsis comprises a single species, S. sinensis, endemic to China. The genus is currently placed in the Amblystegiaceae, solely on the basis of gametophytic characters since its sporophytes are unknown. As a semiaquatic plant, the character of a strong leaf costa and marginal borders can aid S. sinensis to adapt drought as while as aquatic conditions. In this study, the phylogenetic position of Sciaromiopsis was revisited based on morphological and molecular phylogentic evidences of three datasets, the plastid rps4 dataset with 346 mosses species, the ITS dataset with 104 moss species and 82 plastid protein-coding gene dataset with 32 moss species. According to the morphological characters of gametophyte, the stable pattern of pseudoparaphyllia, leaf cells smooth and single costa of Sciaromiopsis are consistent with key characteristics of the Brachytheciaceae, the ovate-lanceolate leaves, differentiated alar cells and rhomboidal median leaf cells are consistent with key characteristics of the Brachythecium. Maximum likelihood and Bayesian analyses of both datasets of the rps4 gene and the 82 plastid protein-coding genes clearly indicated that Sciaromiopsis is a member of Brachytheciaceae. Sciaromiopsis sinensis is either clustered in a well supported clade among species of Brachythecium, Koponeniella and Myuroclada in the rps4 tree, or strongly supported as the sister to Brachythecium rivulare in plastid 82 gene tree. Maximum likelihood analysis of the nuclear ITS locus suggested that S. sinensis is nested within Brachythecium with moderate support. Thus, S. sinensis should be considered as a member of the Brachythecium, the diagnostic character of its leaf margin bordered by 5–8 rows of linear cells making it an easy distinction from other species of Brachythecium.