Evolutionary and taxonomic relationships of Acacia s.l. (Leguminosae: Mimosoideae)

The species of Acacia s.l. are currently undergoing a taxonomic upheaval. This is due, in large part, to recent molecular work that has confirmed previous morphological studies and concluded that the genus is not monophyletic. At least five monophyletic lineages have been defined within the genus and, largely on the basis of molecular data, these are distributed throughout the tribes Acacieae, Ingeae and Mimoseae of the Mimosoideae. We provide new and review previous molecular data used to redefine the generic classification of the genus into five segregate genera. The present study doubles the number of plastid base pairs compared with previous studies, to over 7 kb of aligned sequence. These data confirm previous clades and the present is the first to identify robust support for relationships among clades on the backbone of the phylogeny. The support for Vachellia is stronger than for any subclade within it. However, the support for Senegalia s.s. is weaker than it is for each of two subclades within it. There is no support for the former tribal classification with the enlarged dataset. The nomenclatural implications of which clades are recognised at a generic level are discussed.