A taxonomic revision of the Malesian species of Lasianthus (Rubiaceae)

Based on herbarium collections, the Malesian species of the genus Lasianthus are revised. A total of 131 species including 5 subspecies and 6 varieties are recognized from the Malesian region, of which 41 species, 3 subspecies and 3 varieties are described as new, and 3 new combinations are made for varieties. 22 species names and 15 variety names are reduced to synonyms. Ten species names and 2 varieties are treated as dubious mainly because their types cannot be traced. Additionally, 11 species are further excluded from Lasianthus. All species are described and a key to Malesian Lasianthus is given.