Detailed descriptions, habitat preferences, geographic range, and representative specimens are given for the 13 native and two introduced taxa of Acacia subgenus Acacia (approximately the same as Acacia series Gummiferae) that are found in the South American flora. Some of these taxa are wide ranging. Acacia macracantha, A. tortuosa, and A. farnesiana are extremely common in northern South America, whereas A. caven and A. aroma occur throughout much of the southern half of the continent. The remaining species have restricted ranges, being found in relatively small areas. Principal components analysis (PCA) of vegetative and floral features shows that these species form discrete groups in plots of the first three principal components. From these data, most of the species were found to be relatively homogeneous, as indicated by the tight clusters formed in the PCA plots. In contrast, A. macracantha, a species ranging from Florida, south through the Caribbean, into South America, and in Mexico, is highly variable morphologically. The data suggest little gene flow between species. Hybrids are extremely uncommon.

Communicating Editor: Matt Lavin