Radula subacuminata, a new epiphyllous species of Radula (Marchantiophyta) from China and Vietnam

Radula sect. Epiphyllae is a pantropical section of subg. Metaradula, often growing on the surface of living leaves and with occurrence of gemmae on leaf lobes. Its taxonomic status was once in controversy centered on which subgenus it belonged to and whether it was monophyletic. We describe Radula subacuminata, a new epiphyllous species from China and Vietnam based on morphological and molecular evidence. Phylogenetic analyses of combined molecular datasets (trnG, trnL-F, rps4 and atpBrbcL) with maximum parsimony, maximum likelihood and Bayesian methods reveal that R. subacuminata belongs to sect. Epiphyllae and has close relationships with R. acuminata, R. grandilobula and R. protensa, three other epiphyllous species all bearing gemmae on the surface of leaf lobes. A PCA analysis of morphological traits indicates these four taxa are distinctive groups. The results also confirm that sect. Epiphyllae is monophyletic and should be retained. A preliminary key to 18 species in sect. Epiphyllae is provided.