A taxonomic revision of the genus Leptocereus (Cactaceae) in Haiti and the Dominican Republic

Until recently the genus Leptocereus (Cactaceae) had been little studied on Hispaniola, an island in the Caribbean shared between Haiti and the Dominican Republic. For many years only three endemic species were accepted as being present: Leptocereus paniculatus (equivalent to Neoabbottia paniculata), L. undulosus (equivalent to Dendrocereus undulosus) and L. weingartianus. The identity of L. weingartianus is obscure and the type material is a seedling plant, originating from seed collected in Haiti, showing juvenile characters and lacking flowers or fruits. For many years this name was applied to all Leptocereus on the island of Hispaniola excluding L. paniculatus and L. undulosus, although two recently published species (L. demissus and L. velozianus) have been segregated from it. We propose that the likely identity of the type material of L. weingartianus is a seedling of L. paniculatus but due to the designation of an epitype we retain the name for a thin stemmed species found in south-central Hispaniola. Based on fieldwork in Haiti and the Dominican Republic supplemented with analyses of seed and seedling morphology at Gibraltar Botanic Gardens, we recognise nine species, all endemic to Hispaniola, including four which are described here for the first time (L. rosei sp. nov., L. bayahibensis sp. nov., L. cremnophilus sp. nov., and L. septentrionalis sp. nov.). We provide a key to the species and, for all taxa, we supply a description, distribution map, iconography, list of specimens studied and photographic plates. We also propose three subgenera for Leptocereus (subgenus Leptocereus, subgenus Dendrocereus, and subgenus Neoabbottia), the latter two based on genera of the same names. All species from Hispaniola belong to Leptocereus subgenus Neoabbottia except for L. undulosus, which is a member of Leptocereus subgenus Dendrocereus.