Abstract
Murdannia (Commelinaceae), consisting of some 60 species, is unusual in the family in having both actinomorphic and zygomorphic flowers usually with the median petal on adaxial side, and having either two or three antisepalous stamens. To understand floral evolution in the genus in light of a phylogenetic context, we conducted phylogenetic analyses of 18 species and one cultivar mainly from Asia using plastid DNA sequences, then examined their respective floral morphology. The results showed a monophyly of all 16 Asian species of Murdannia and one cultivar, and of the ten species with zygomorphic flowers. Comparisons with flowers of related genera suggest that great morphological changes occurred early in the evolution of Murdannia, including rotation of a symmetrical plane by 60 degrees so that the median petal of the flowers is positioned at the top on the adaxial side. Within the genus, a change in floral symmetry from actinomorphy to zygomorphy occurred one time and was accompanied by androecial zygomorphy resulting from replacement of one of three antisepalous stamens by a staminode. Additionally, the two latero-abaxial petals usually spread laterally around 160–180 degrees. The infrageneric classification of the Asian species is also briefly discussed.
