Macaranga is a genus in the family Euphorbiaceae. It comprises trees, treelets and some lianas, many of which are conspicuous large-leafed pioneers of disturbed habitats. Some species have ant associations. There are 257 species, of which 21 are newly described here. The genus is most diverse in South East Asia and New Guinea but also occurs in Africa and Madagascar (37 species), continental Asia (30 species), the Pacific Islands (24 species) and Australia (7 species). The species can be identified with the help of either regional keys or keys within informal species groups. Twenty-five species are illustrated.
T.C. Whitmore (1935-2002) was an ecologist and forest botanist who specialised in South East Asian rain forests. His interest in Macaranga started when he first visited the Malay Peninsula in the 1960s and noticed the remarkable ecological and morphological adaptations of these plants. He maintained this interest throughout his career. This prodromus represents an initial overview of the systematics of this genus; sadly he died before he could finish it. His friends Peter Ashton (Harvard University) and Terry Pennington (Royal Botanic Gardens, Kew) agreed to work with his widow, Wendy, to complete the work. Gordon McPherson (Missouri Botanical Garden) contributed the Madagascan key and species accounts, Mike Lock (Royal Botanic Gardens, Kew) contributed accounts of some African species and Stuart Davies (Arnold Arboretum, Harvard University) two species from Borneo. Treatments of two Asian sections of Macaranga published separately by Davies are referred to here.