Riccia boumanii Dirkse, Losada & M. Stech sp. nov. (Ricciaceae, Marchantiophyta) in the Canary Islands, the first species of Riccia subgenus Riccia section Pilifer Volk outside South Africa

A morpho-molecular study was undertaken to solve the taxonomic identity of Riccia plants from the Canary Islands. These plants were assumed to belong to the South African endemic Riccia section Pilifer, but could not be assigned to a particular species in that section. In the interim they were named R. lamellosa (section Riccia), since R. lamellosa is the only European species with conspicuous white ventral scales. Molecular phylogenetic reconstructions based on trnL-F and ITS2 sequences confirmed that the respective Riccia plants belong to section Pilifer. The respective clade is clearly separated from the clades of R. lamellosa and R. elongata, the latter being morphologically most similar within section Pilifer. Based on the combined molecular and morphological evidence the Riccia plants from Canary Islands are described as a new species, R. boumanii, which represents the first species of section Pilifer outside South Africa. Based on revised herbarium specimens, R. boumanii occurs on five islands of the Canary Islands archipelago, namely El Hierro, Gran Canaria, La Gomera, La Palma, and Tenerife.