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This work presents a monographic revision of the genus Acalypha L. (Euphorbiaceae) from the Western Indian Ocean Region, including Madagascar, the Comoros Archipelago, the Mascarene Islands, the Seychelles Archipelago, and the Scattered Islands. Forty-nine species are recognized, with 42 native and seven probably introduced; 39 are found in Madagascar, eight in the Comoros, eight in the Mascarene Islands, four in the Seychelles, and one in the Scattered Islands. For each species, we provide a description, information about distribution and habitat, a distribution map, and a preliminary conservation assessment. Original illustrations and the first identification key for Acalypha species of this region are also included. Lectotypes are designated for 10 names. Acalypha crateriana (Coode) I.Montero & Cardiel, comb. nov. is proposed as a new combination and Acalypha berryi I.Montero, Cardiel & G.A.Levin, sp. nov., a new species from Mayotte, is described and illustrated.
Euphorbiaceae, Acalypha, Madagascar, Comoros, Seychelles, Mascarene Islands, brachyblast, lectotypifications, new synonyms, new combination, new species