Molecular phylogenetics of Acacia subgenera Acacia and Aculeiferum (Fabaceae: Mimosoideae), based on the chloroplast matK coding sequence and flanking trnK intron spacer regions

The genus Acacia is subdivided into the following three subgenera: subg. Acacia, subg. Aculeiferum and the predominantly Australian subg. Phyllodineae. Morphological and molecular studies have suggested that the tribe Acacieae and genus Acacia are artificial and have a close affinity to the tribe Ingeae. Sequence analysis of the chloroplast trnK intron, including the matK coding region and flanking non-coding regions, were undertaken to examine taxon relationships within Acacia subgenera Acacia and Aculeiferum. Subgenus Acacia is monophyletic while subgenus Aculeiferum is paraphyletic. Within the subgenera, major divisions are found based on biogeography, New World versus African-Asian taxa. These data suggest that characters such as inflorescence and prickle and/or stipule type are polymorphic and homoplasious in cladistic analyses within the subgenera.