Floral ontogeny in Cordyla pinnata (A. rich.) Milne-Redh. (Leguminosae, papilionoideae): Away from stability

Abstract

Most representatives of the third largest angiosperm family, Leguminosae, share monosymmetric flowers with a precisely defined number and morphology of all parts especially the corolla. However, in some lineages monosymmetry is lost. This alteration is usually associated with an increase of variation in number of floral organs. This paper reports the results of a survey on floral ontogeny in African basal papilionoid legume Cordyla pinnata. The flowers of this tree are polysymmetric (except for the carpel, if single), having a completely closed calyx which typically initiates as three lobes, no corolla, a polymerous androecium, and a gynoecium which is sporadically multicarpellate. Cordyla exhibits some similarity of floral traits with swartzioid legumes (Swartzia p.p., Bocoa) rather than with its nearest phylogenetic surrounding. Some features of convergence between Cordyla and mimosoid legumes are also remarkable, such as a showy polymerous androecium and anther glands. This species is an example of an evolutionary trend towards destabilization of the flower structure. Supernumerary carpels seemingly lack any adaptive value and represent a kind of ontogenetic overexpression.