A review of the genus Diplophyllum (Marchantiophyta) in North and East Asia with the description of a new species (D. sibiricum) based on integrative taxonomy

Diplophyllum sibiricum is described based on plants from North and East Asia. It somewhat resembles D. obtusifolium, from which it differs in coloration and highly protandrous paroecy, as well as distribution. The species status of D. trollii is confirmed based on molecular studies, and it is additionally recorded from the spurs of the Himalaya in Guizhou Province of China. Both taxa are slightly molecularly divergent ‘young’ species that are strongly defined geographically from close morphological relatives. Diplophyllum obtusatum and D. obtusifolium should be excluded from the flora of North Asia. A key to Diplophyllum taxa in North and East Asia is provided. Probable cryptic speciation was observed within D. albicans, but this problem is regarded as requiring further studies. The split of Diplophyllum subg. Diplophyllum into two sections is not maintained.