Phylogenetic analysis of Acacia (Mimosaceae) as revealed from chloroplast RFLP data

Chloroplast DNA of 22 species of Acacia (Tourn.) Miller was digested with t en restriction endonucleases, Southern-blotted and probed with cloned fragm ents covering the chloroplast genome of tobacco (Nicotiana tabacum L.). Phy letic and phenetic analyses of the resulting 176 polymorphic bands recorded among the 22 species were performed. The phylogram was reconstructed using heuristic search and Wagner parsimony. The resulting most parsimonious con sensus phylogram displayed three major phyletic lineages, consistent with t he previously established three subgenera of Acacia. The 10 species of subg enus Acacia and the 6 species of subgenus Heterophyllum formed two monophyl etic sister clades. The 5 species of subgenus Aculeiferum studied and Acaci a albida (Syn. Faidherbia albida) grouped together and were basal to the cl ades of subgenera Acacia and Heterophyllum. The phylogram indicated that su bgenus Heterophyllum diverged earlier from subgenus Aculeiferum than did su bgenus Acacia; however, the phenogram indicated the reverse. The study indi cated that A. nilotica and A. farnesiana are sister species, though A. nilo tica is Afro-Asiatic and A. farnesiana is American. The phenogram separated the three subgenera in agreement with the phylogram, but the two dendrogra ms differed regarding the topologies of the species and the distance of evo lution between subgenera Acacia and Heterophyllum.