Melastoma is revised for Peninsular Malaysia and Singapore. Nine species and one new variety are recognised for Peninsular Malaysia, of which two species also occur in Singapore (M. malabathricum L. and M. molle (C.B.Clarke) Wall. ex Cogn.). Ten lectotypes are designated. Three species are so far only known from Peninsular Malaysia and nowhere else: M. longisepalum Ridl., M. kemamanense L.Neo & K.M.Wong, and M. scabrum Ridl.
Hypanthium scale type is used foremost for delimiting species in combination with characters of the vegetative organs. Character-state combinations present in the greatest number of collections are interpreted to represent natural species, while less common instances of mixed character-state combinations are interpreted as putative hybrids or introgression products.
Two-species hybrid combinations are identified between one species postulated to have contributed hypanthium scale characters and a second species postulated to have contributed other characters such as hypanthium size, twig scale type, leaf surface indumentum, etc; these are described between M. malabathricum and M. muticum Ridl., M. malabathricum and M. sanguineum Sims, and M. muticum and M. velutinosum Ridl. Furthermore, non-typical forms (infraspecific variants) are recognised in M. malabathricum, M. muticum, and M. sanguineum, which differ from the typical forms of the species by a single character.
Naturally-occurring floral mutants which have been observed in Melastoma species in Peninsular Malaysia are also briefly described and discussed. An identification key to species, and descriptions of species and putative hybrids or introgression products, are given.
This is followed by a chapter which presents an investigation into the molecular basis for some of the Peninsular Malaysia and Singapore species, putative hybrids or introgression products, which found preliminary support for the morphology-based taxonomic concepts of the present revision. This work should provide the foundation for future work on hybridisation in Melastoma in the region.
Finally, a comprehensive overview is given of ethnobotanical uses of Melastoma in the region, especially of M. malabathricum.
