LUCKOW, MELISSA1*, JOSEPH T. MILLER2, DANIEL J. MURPHY3, and TATYANA LIVSHULTZ1. 1L. H. Bailey Hortorium, 462 Mann Library, Cornell University, Ithaca, NY 14853 USA; 2Biology Department, 138 Biology Building, University of Iowa, Iowa City, IA 52242-1324, USA; 3School of Botany, University of Melbourne, Parkville, Vic. 3052 Australia. - A cladistic analysis of the subfamily Mimosoideae, Leguminosae, based on data from the chloroplast genes trnL and matK.
Until very recently five tribes have been recognized in the
Mimosoideae, based primarily on combinations of a few characters:
number and fusion of stamens and aestivation and fusion of the sepals.
The Parkieae, Mimozygantheae, and Mimoseae were distinguished as
having 10 stamens (considered plesiomorphic in the Mimosoideae): the
Parkieae with imbricate aestivation of the fused calyx lobes; the
Mimozygantheae with free, imbricate sepals; and the Mimoseae with the
sepals valvate. The Acacieae and Ingeae, also with valvate aestivation
of sepals, have either many free (Acacieae) or many fused (Ingeae)
stamens. That these groups might not be natural has long been
recognized, but improved classifications are only now beginning to
emerge. This study combines data from several independent molecular
studies of the tribes to improve our understanding of the
relationships among mimosoid genera. Over 140 taxa were sampled. The
chloroplast genes trnL and trnK/matK served as data sources for
phylogeny reconstruction. Parsimony analysis of the data resulted in
11,326 most parsimonious trees. None of the tribes are monophyletic on
the strict consensus tree. The Mimoseae are paraphyletic, with members
of all other tribes derived from within it. The Parkieae are
polyphyletic, with Parkia nested among the Piptadenia group in the
tribe Mimoseae. The Acacieae and Ingeae are polyphyletic and form two
clades. Acacia subg. Acacia is strongly supported as monophyletic, and
is not closely related either to other species of Acacia s.lat. or the
Ingeae. The remainder of the Acacieae and Ingeae form a monophyletic
group, with the Australian acacias (subg. Phyllodineae) also strongly
supported as a monophyletic group. Acacia subg. Aculeiferum is
paraphyletic. Relationships among the Ingeae are poorly resolved and
not well supported. This study highlights the inevitability of
recognizing segregate genera from Acacia s. lat., and the necessary
abandonment of Bentham's longstanding tribal classification.
Key words: Acacia, Leguminosae, MImosoideae, phylogeny