Pollen morphology and phylogeny of the tribe Tabernaemontaneae (Apocynaceae, subfamily Rauvolfioideae)

Both the tribe Tabernaemontaneae and the genus Tabernaemontana have been much discussed concerning delimitation and classification. In the present paper, the pollen morphology of Tabernaemontaneae s.l. is studied with light and scanning electron microscopy (SEM), and compared with the results of a phylogenetic analysis of molecular data. No pollen morphological synapomorphy was found supporting the monophyly of the tribe Tabernaemontaneae s.l. The monophyly of Tabernaemontaneae s.str. is supported by the occurrence of distinctly lalongate endoapertures that might be fused to form an endocingulum. Although the endocingulum does occur in some Old World species, it is interpreted as a synapomorphy of the New World species, which make up a monophyletic group according to molecular data. The inclusion of the genus Stemmadenia in the New World clade within Tabernaemontana is fully supported by pollen morphology. The Old World Tabernaemontana clade is supported by the occurrence of densely perforate pollen with long colpi.