The Macaronesian Liverwort Riccia boumanii Dirkse, Losada & M.Stech (Marchantiophyta: Ricciaceae) Confirmed New to Asia by Morphological and Molecular Evidence

Riccia L. is the largest genus of complex thalloid liverworts with over 250 species currently accepted. Riccia boumanii Dirkse, Losada & M.Stech (Ricciaceae) has been considered to be endemic to the Canary Islands, Spain. Morphological evidence and molecular-phylogenetic analyses based on sequences of nuclear ribosomal ITS2, plastid rbcL, and plastid trnL-F confirm that this species occurs in Gansu and Sichuan, China. Riccia boumanii represents the first species of section Pilifer Volk of the genus in Asia. The low values of p-distances (0% for trnL-F-region, and 1.6% for ITS2-region) reveal that R. boumanii bears a low level of divergence. Micrographs, a distribution map and descriptions based on the Chinese plants are provided. The range extension of Riccia boumanii suggests that more taxa of Riccia may have a wider distribution.