A partial revision of the Hippomaneae (Euphorbiaceae) in Malesia

The Hippomaneae (Euphorbiaceae) are revised for Malesia. Only Excoecaria and Homalanthus are excluded. A key to all Malesian genera is provided. The generic concepts applied differ markedly from previous treatments for the region with the following genera accepted: Balakata, Falconeria, Gymnanthes, Microstachys, Sapium, Shirakiopsis, Stillingia and Triadica. All of these genera show peculiarities in biogeography and ecology, which are discussed. Among these genera only Stillingia is kept as traditionally used. Balakata (based on Sapium sect. Pleurostachya) and Shirakiopsis (based on Sapium sect. Parasapium but excluding its type) are described as new genera; Falconeria, Microstachys and Triadica are re-established as distinct genera having been treated as Sapium sect. Falconeria, Sebastiania sect. Microstachys and Sapium sect. Triadica for a long time. Gymnanthes is cited for the first time in Malesia based on two former species of Sebastiania, and the African genus Duvigneaudia is united with it. Sapium and Sebastiania are no longer considered as indigenous to Malesia, with Sapium (= Sapium sect. Americana) formerly being cultivated. Altogether 13 species are accepted in the present revision. No new species are described, but only two of the well-known names are accepted as previously used (Sapium glandulosum, Stillingia lineata subsp. pacifica). Numerous new combinations are proposed in the present revision: Balakata baccata, Balakata luzonica, Gymnanthes borneensis, Gymnanthes inopinata, Gymnanthes remota, Shirakiopsis indica, Shirakiopsis sanchezii, Shirakiopsis virgata. Several other, previously available but uncommon names are re-introduced, namely Falconeria insignis, Microstachys chamaelea, Triadica cochinchinensis (the correct name for the former Sapium discolor), and Triadica sebifera. Finally, two new synonyms are proposed by uniting Sebastiania lancifolia with Gymnanthes borneensis, and Sapium plumerioides with Stillingia lineata subsp. pacifica. Lectotypes are selected for eight names.