XVI International Botanical Congess

Pollen of the Afro-Malagasy genus Aristea (ca. 50 spp.) is among the most diverse of Iridaceae subfam. Nivenioideae. Four types are distinguished: mono-, tri- and dizona-sulcate, and sulculate. Cladistic analysis shows 3 major groups, with the monosulcate type plesiomorphic. Comparison of pollen and molecular data suggested that Nivenioideae are paraphyletic. Ultrastructural study shows important variation in the exine layers, the intine is typically 3-layered, the channelled median layer playing an important role during germination. Ontogenetic study of some spp. indicates the presence of a rudimentary endexine. Results are discussed with respect to cladistic relationships.