Phylogenetic position of Cyathodium indicum (Cyathodiaceae, Marchantiophyta), a rare Indian liverwort newly found in China

Introduction: Cyathodium is a small pantropical complex thalloid liverwort genus (Marchantiopsida) with 13 species currently accepted worldwide. Cyathodium indicum is the only species whose spores are typically in diads with baculate-tuberculate projections, and it was previously known only from the northwestern Himalayas of India. However, it has never been phylogenetically investigated using molecular data. Methods: Morphological characteristics were investigated by microscopic examination of the Chinese collections. The phylogenetic position of Cyathodium indicum was evaluated based on three plastid markers (psbA, rbcL and rps4). Key results and conclusions: Cyathodium indicum is newly reported for China. Phylogenetic analyses reveal that two Chinese samples of C. indicum form a well-supported clade within the subgenus Cyathodium, positioned as the sister group to C. aureonitens + C. tuberosum. Both subgenus Cyathodium and subgenus Metacyathodium were identified as monophyletic groups. The occurrence of C. indicum in Yunnan, China, suggests that more populations might be found in China and the Himalayas.