A taxonomic revision of the Malesian genus Trigonopleura Hook.f. (Euphorbiaceae)

Trigonopleura, a genus from W Malesia, has three species, the widespread T. malayana (Malay Peninsula, Sumatra, Borneo, Sulawesi) and the two endemic species T. dubia (Philippines) and T. macrocarpa (Sarawak, Kuching). The species differ slightly from each other in leaf size, colour, and margin, flower and fruit size, fruit wall thickness, and aril size. A phylogenetic analysis was not performed, but it is argued that both endemic species split off separately from T. malayana. Trigonopleura is probably related to Chaetocarpus, in particular to C. castanocarpus. Probably, Chaetocarpus is a paraphyletic group of species and will be monophylitic when united with Trigonopleura, but this will need thorough phylogenetic research. Here, both genera are kept separate, because they are very distinct (see Table 1). Typical for Trigonopleura are the fruits (wrinkled when dry, tomentose), the seeds (arillate), the inflorescences (axillary clusters of flowers), and the flowers (sepals imbricate, petals present, valvate, disc lobed, an androphore, 3 locules with one ovule each).