Endemic families of Madagascar. VI. A synoptic revision of Rhodolaena (Sarcolaenaceae)

As part of the reevaluation of the taxonomic frameworks of the vascular plant families endemic to Madagascar and the Comoro Islands prior to an assessment of their conservation status, a synoptic revision is presented of Rhodolaena (Sarcolaenaceae). Recent molecular sequence data suggest that Sarcolaenaceae are sister to Dipterocarpaceae in an expanded Malvales. Within the family, Rhodolaena appears to be closest to Schizolaena, with which it shares flowers usually borne in pairs subtended by an involucre that is indistinct or collar-like at anthesis but then expands very late to become somewhat fleshy and surround the woody, capsular fruit. Rhodolaena differs from Schizolaena by its solitary inflorescences with long, pendulous peduncles and flowers with 5 sepals versus branched inflorescences and flowers with 3 sepals in Schizolaena. Seven species are recognized, three of which are described as new (R. coriacea, R. leroyana, and R. macrocarpa). A key to the species is provided in English and French.