A synopsis of the Malagasy endemic genus Megistostegium Hochr. (Hibisceae, Malvaceae)

A synopsis of the endemic Malagasy genus Megistostegium (Malvaceae) is presented based on material from herbarium specimens and field observations. Principle Components Analysis, using measurements from herbarium specimens throughout the range of the genus and vegetative measurements from one site of sympatry where all three species grow in close proximity, assigns the accessions of Megistostegium to three distinct clusters that differ dramatically in habit, leaf size and shape, flower size and morphology. These correspond to the three traditionally delimited species and these morphological boundaries appear to be maintained despite gene flow. A key to the species is presented and pollen characters, ethnobotanical uses and conservation status are also included.