A PHYLOGENETIC ANALYSIS OF THE MIMOSOIDEAE (LEGUMINOSAE) BASED ON CHLOROPLAST DNA SEQUENCE DATA

A phylogenetic analysis of 134 exemplars of Mimosoideae and seven caesalpinioid outgroups was conducted using chloroplast DNA sequence data. Characters were drawn from the trnL and trnK intron and spacer regions, as well as the matK coding sequence. Parsimony analysis of the data resulted in 21,240 most parsimonious trees. None of the tribes of Bentham (1875) are monophyletic on the strict consensus tree. Parkieae are polyphyletic, with Parkia more closely related to various Ingeae and Mimoseae than to Pentaclethra. Tribe Mimoseae forms a paraphyletic grade in which are embedded both Acacieae and Ingeae. The genus Acacia s.l. is not monophyletic. Acacia subg. Acacia (Acacia s.s) is strongly supported as monophyletic, and is not closely related either to other species of Acacia s.l. or the Ingeae. The remainder of the Acacieae and Ingeae form a monophyletic group, with the Australian acacias (segregate genus Racosperma or Acacia subg. Phyllodineae) also strongly supported as a monophyletic group. Acacia subg. Aculeiferum (Senegalia) is paraphyletic. Relationships among the Ingeae are poorly resolved and not well supported. This study highlights the inevitability of recognising segregate genera from Acacia s.l., and the necessary abandonment of Bentham’s longstanding tribal classification.