Based on the most recent revision, the Bouteloua curtipendula
complex is a group of 11 grass species and 5 varieties native to the
New World. Non-coding nuclear ribosomal and chloroplast DNA sequences
(ITS and trnT-L-F regions, respectively) subjected to parsimony
cladistic analysis show that the complex is monophyletic, though most
of the species are para- or polyphyletic. Both phylogenies have three
major clades. The largest clade includes mostly polyploids with more
than one spikelet per branch and usually orange, red, or purple
anthers. The other two clades group mostly diploid taxa with yellow
anthers, however the number of spikelets per branch varies from one to
many. The phylogenies suggest that diploidy is ancestral. Samples
showing incongruencies between the ITS and trnT-L-F phylogenies
were found to be polyploids and in possession of several different
copies of the ITS region, indicating that hybridization via
allopolyploidy has played a role in the diversification of the
complex. Homoplasy, hybridization, polyploidy, and the reported
occurrence of apomixis combine to make circumscription of taxa in this
group challenging.
Key words: allopolyploidy, Bouteloua curtipendula, evolution, gramineae