Molecular, morphological, and phytochemical evidence for a broad species concept of Plagiochila bifaria (Hepaticae)

Debate over the synonymy of the European Plagiochila killarniensis and the Neotropical P bifaria of R sect. Arrectae has focused on differences in secondary metabolite composition. The broad morphological species concept of R bifaria proposed in recent papers has now been tested by comparing nrDNA ITS1 and ITS2 sequences of R bifaria populations encompassing several different morpho- and chemotypes from the British Isles, Tenerife, Costa Rica, Brazil, Ecuador, and Bolivia, with sequences of other species of R sects. Arrectae, Rutilantes, and Fuscoluteae. Phylogenetic analyses demonstrate that specimens of P. bifaria form a well supported clade within Plagiochila sect. Arrectae. Sequences of R bifaria from the British Isles, Tenerife, and Ecuador, representing the "methyl everninate" chemotype, form a well supported subclade within the P bifaria clade. Sequences of specimens from Costa Rica, Brazil, and Bolivia are placed in the basal part of the R bifaria clade. The data support a broad species concept of P bifaria. The different chemotypes do not warrant distinct taxonomic ranks. Plagiochila centrifuga and P. compressula are treated as new synonyms of R bifaria.