A revision of Dombeya subsect. Rigidae, which comprises two Malagasy species (D. linearifolia and D. rigida), is presented. The classification of these species within Dombeya is preferred to an alternate placement within Helmiopsis. Three subspecies of D. rigida are recognized: subsp. parvifolia, characterized by small leaves, is newly described, and subsp. guazumifolia is newly recognized at that rank. Arènes’ two subspecies of D. linearifolia are synonymized, and a new subsp. muricata, characterized by fruit similar to that of D. rigida, is described. Both species display considerable variation in leaf and fruit morphology in the north, but variation is discontinuous, indicating that the species are usually reproductively isolated.
Malvaceae, Dombeya, Helmiopsis, Madagascar, new subspecies