Four new combinations in Chomelia and Stenostomum (Rubiaceae, Guettardeae) from Central America, the Guianas and the Amazon Basin

According to current generic delimitations, supported by wood anatomy, palynology, and recent molecular phylogenies, Antirhea, traditionally treated as a Pantropical genus, is instead restricted to the Paleotropics. At the same time, the Neotropical species traditionally positioned in Antirhea should be positioned in Stenostomum. Following these definitions, Stenostomum is a genus with most of the species present in the Caribbean Region, and two species present in the Guianas, namely S. acreanum and S. guianensis, distributed throughout the Amazon Basin. In addition, according to these new generic delimitations, two species previously positioned in Guettarda and Antirhea need to be transferred to Chomelia, as C. triflora and C. ulei.