Soella (Marchantiophyta: Lejeuneaceae), a new genus from China and Japan

Lejeuneaceae is the largest family of liverworts with over 1800 species distributed mostly in moist tropical and subtropical regions. Drepanolejeunea (Spruce) Steph. is the fourth largest genus of this family with over 120 species currently listed in the updated checklist of liverworts and hornworts, however no phylogenetic studies of this genus based on an extensive taxon sampling have been done. Here we for the first time elucidate phylogenetic relationships of Drepanolejeunea by using the nuclear ribosomal ITS region and two chloroplast regions (rbcL, trnL-trnF). Our molecular phylogenetic results reveal that Drepanolejeunea as currently circumscribed is not monophyletic. On the basis of the combined molecular phylogenetic and morphological data, a new genus in the subtribe Lepidolejeuneinae, Soella, is proposed to include the remarkable and rare species, Drepanolejeunea obtusifolia T.Yamag. previously known from Japan. Drepanolejeunea subg. Acantholejeunea R.M.Schust. (≡ Acantholejeunea (R.M.Schust.) R.M.Schust.), one of five subgenera currently accepted in Drepanolejeunea, is suggested to be synonymous with Ceratolejeunea (Spruce) J.B.Jack et Steph. Soella obtusifolia (T.Yamag.) R.L.Zhu et al. comb. nov. and Ceratolejeunea spinistipula (Herzog) R.L.Zhu et al. comb. nov. are proposed. Drepanolejeunea tenera K.I.Goebel is new to the liverwort flora of China. With the description of Soella, the liverworts (Marchantiophyta) so far contain 369 genera, including 73 genera belonging to Lejeuneaceae.