Abstract
Four new species of Acalypha (Euphorbiaceae, Acalyphoideae) from the Western Indian Ocean Region, based on morphological and molecular evidence, are described, illustrated, and mapped. Acalypha gillespieae sp. nov., A. leandrii sp. nov. and A. nusbaumeri sp. nov. are endemic to Madagascar, and A. mayottensis sp. nov. is known only from Mbouzi islet (Mayotte), in the Comoros Archipelago. We also describe for the first time in Acalypha the presence of membranous or chartaceous perules covering the axillary buds. Preliminary conservation assessments of the new species are also provided.