Omphalea (Euphorbiaceae) in Madagascar: A new species and a new combination

Omphalea ankaranensis, a shrub endemic to limestone karst hills of northern Madagascar, is described and illustrated. The species is closely related to Omphalea palmata Leandri of western Madagascar but differs in its entire to coarsely crenate-dentate leaf blade margins, broader inflorescence bracts, lax cymules, and shorter pistillate flower pedicels. The new combination Omphalea oppositifolia (Willdenow) L. J. Gillespie is made for the widely distributed rainforest species of eastern Madagascar, previously known as Omphalea biglandulosa Persoon. A synopsis including new lectotypifications and a key to the four Madagascan species of Omphalea is provided.