Floral development and phylogenetic position of Schismatoglottis (Araceae)

In the inflorescence of Schismatoglottis, atypical sterile flowers are present between the male and female zones. Contrary to what occurs in Cercestis and Philodendron, where the atypical flowers are bisexual, in Schismatoglottis the atypical flowers consist of aberrant male or female flowers. These atypical unisexual flowers have different forms depending on their position in the inflorescence. The atypical flowers located near the male zone share characteristics with staminate flowers, and those located near the female zone have features in common with pistillate flowers. The developmental pathway of atypical flowers in Schismatoglottis is already channeled in the direction of female or male flowers before the appearance of aberrant appendages. Interpistillar sterile structures located in the female zone correspond to modified female flowers. The systematic position of Schismatoglottis is not fully resolved on a molecular phylogenetic analysis of 45 genera of Araceae, on the basis of chloroplast trnL intron and trnL‐F intergenic spacer sequences. The floral ontogenetic pattern in Schismatoglottis represents a different pathway in the evolution of unisexual flowers in the subfamily Aroideae.