Systematics and taxonomy of the tribe Sipaneeae (Rubiaceae)

The tribe Sipaneeae (Rubiaceae) includes 10 genera and 44 species, and has its centre of diversity on the Guiana Shield (northern South America), where 9 of the 10 genera occur. Only 4 species of Sipanea and Limnosipanea are also present on the Brazilian Shield, while Steyermarkia, Sipanea and Limnosipanea are present in Central America with one species each. The genera Sipaneopsis, Chalepophyllum, and Dendrosipanea are endemic to white sand areas of the Amazon Basin. The habit in the tribe Sipaneeae ranges from herbs (terrestrial, amphibian or rarely aquatic), subshrubs, shrubs to treelets. Within the tribe is present a wide variation in flower morphology, and in Sipaneopsis is present a unique flowering mode in flowering plants. Within the tribe, four genera are heterostylous, while the others are homostylous. Several recent articles have been dedicated to the description of new species in this tribe. For all the taxa of this tribe, full synonymy, typification, description, ecological observations, geographic distribution, illustrations, and IUCN conservation assessment were presented in a recently published monographic treatment.