Abstract
Melicope oppenheimeri K.R. Wood, Appelhans & W.L. Wagner (section Pelea (A. Gray) Hook. f., Rutaceae), a rare endemic tree from West Maui, Hawaiian Islands, is described and illustrated with notes on its ecology, conservation, and phylogenetic placement. The new species differs from Hawaiian congeners by its carpels basally connate 1/5, narrowed into a strongly reflexed beak 10-15 mm long. It also differs in a combination of leaves with 7-10 pair of secondary veins; cymes to 3 cm long; peduncles 5-6.5 mm long; flowers perfect; capsules 4-9 × 40-52 mm; and a densely appressed short-sericeous ovary. Melicope oppenheimeri is known only from an isolated cliff-base plateau in upper Waihe'e Valley, West Maui. Its discovery brings the number of recognized Melicope J.R. Forst. & G. Forst. species in the Hawaiian Islands to 49. A table is included indicating the conservation status of Hawaiian Melicope and Platydesma H. Mann., which is nested within Melicope sect. Pelea. Melicope oppenheimeri falls into the IUCN Critically Endangered (CR) Red List category.