Macromitrium giraldii Müll.Hal. (Orthotrichaceae) recognised as a species on the basis of morphological and phylogenetic evidence

Macromitrium giraldii Müll.Hal. was previously considered a synonym of M. japonicum Dozy & Molk. Our ongoing research on the genus Macromitrium Brid. has enabled us to identify morphological differences between M. japonicum and M. giraldii, as well as a close similarity between the latter and the widely distributed East Asian M. cavaleriei Cardot & Thér. Here we present morphological and phylogenetic evidence supporting our speculation that M. giraldii and M. cavarleriei are conspecific, and that the former should be recognised. A morphological study of the original material of Macromitrium giraldii, M. cavaleriei, M. japonicum and their accepted synonyms was conducted, including recent specimens matching their descriptions. A phylogenetic analysis based on the nuclear ITS2 and the plastid trnL–F and trnG regions was performed to investigate relationships within the genus. The morphological and phylogenetic data support Macromitrium giraldii and M. cavaleriei as conspecific, with similarities observed in their branch leaves. All previously accepted synonyms of the latter are additionally confirmed to be M. giraldii. We here propose to synonymise these two species as M. giraldii, since this name has priority. Consequently, M. giraldii is distributed throughout China, as well as in Japan, South Korea, Vietnam, Nepal and India.