Floral ontogenetic evidence in support of the Willdenowia clade of South African Restionaceae

The floral development of a number of representative genera of the Willdeno wia clade of Restionaceae was studied to understand patterns of reduction o f floral elements and sample evidence for discussing the relationships of t he group. All species studied are characterized by a concordant reductive t rend involving the retardation/ reduction of the perianth, the loss of the anterior carpel and the displacement of the remaining carpels, linked with a strongly compressed spikelet. Different modes of carpel reduction, such a s a progressive or immediate loss, or fusion of two neighboring carpels, ar e presented and discussed. The most parsimonious event of gynoecium evoluti on for the Willdenowia clade is either the sterilization of two carpels in an originally trimerous gynoecium, followed by the loss of the anterior car pel, or the sudden loss of the anterior carpel, preceeding the sterilizatio n of one lateral carpel. The concordant development of the taxa of the Will denowia clade supports a one-time loss of a carpel and the homogeneity of t he clade.