Morphological and molecular evidence for a new species, Mannia gradsteinii sp. nov. (Aytoniaceae) from southwestern China

Mannia Corda (Aytoniaceae) is a small complex thalloid liverwort genus with 11 species, which show strongly disjunct and fragmented distributional patterns. China is one of the main centers of distribution for the genus with six species currently known. Mannia gradsteinii sp. nov., a new species from Hengduan Mountains in China, is described and illustrated. It is similar to Mannia triandra (Scop.) Grolle, but differing in the large epidermal pore (72-)136-204 μm in diameter, the smaller spores 47-57 μm with 3-6 irregular areolae across the spore distal surface, the large female receptacles 4.6-8.2 mm in diameter and the air chambers with 2-4 layers. Molecular phylogenetic analysis of the chloroplast gene trnL-F and the large 26S ribosomal DNA subunit confirmed that the new species is a member of Mannia subgenus Neesiella, and sister to M. gracilis (F.Weber) D.B.Schill & D.G.Long, which differs in the presence of a pseudoperianth and the absence of a trilete mark on the spore proximal view.