Abstract
The tribe Posoquerieae was recently described to include the genera Posoqueria Aubl. and Molopanthera Turcz. based on floral morphology, palynology, the presence of the pollen catapult mechanism, and molecular phylogenetic evidence. The floral morphology of these two genera was first recognized as unique in the Rubiaceae by Schumann. Both genera have stamens initially united into an ellipsoidal structure held at an oblique position, with the ventral stamen that springs forward when touched, while the two lateral stamens fold outward. Since their descriptions were published, Posoqueria and Molopanthera have been positioned in several distantly related tribes within the Rubiaceae. The close relationship between the two genera was only recently revealed by molecular phylogenetic studies. The taxonomic history of Posoqueria and Molopanthera is reviewed, and a general morphological comparison (particularly of stamen morphology and pollen catapult mechanism, and observations about pollination biology) of both genera is presented here. The pollen catapult mechanism of Molopanthera is described here in detail for the first time and concluded to be practically identical to that of Posoqueria.