The Role of Phylogenetic Constraints in the Evolution of Pollination Mechanisms in Iridaceae of Sub-Saharan Africa

Novel, specialized systems exploiting bibionid flies, oil-collecting bees, wasps, or crepuscular settling moths as pollen vectors are added to the range of recorded pollination mechanisms in sub-Saharan Africa Iridaceae, while knowledge of the pollination of previously understudied genera such as Aristea, Bahiana, Ferraria, Hesperantha, and Tritoniopsis is expanded. The pollination of 357 species of the sub-Saharan African Iridaceae now includes 17 discrete systems. Based on repetitive interlinked suites of floral attractants and rewards we now infer pollination mechanisms for an additional 883 species. Many pollination systems recur in genera containing \u3e 10 species. The ancestral pollination in African Iridaceae, and also the most common one, involves large, long-tongued bees that contact anthers or stigmas passively while foraging for nectar. Some 182 species (in 11 genera) lack nectar or oil and pollinators forage preferentially for pollen. Our earlier hypothesis that the diversity of pollination mechanisms within a lineage increases via adaptive radiation and/or character displacement involving simple shifts in floral presentation is expanded to include the role of phylogenetic constraint. Specifically, possession of the meranthium flower in Moraea (ca. 195 spp.) and Ferraria (ca. 14 spp.) of subfamily Iridoideae limits the number of pollination shifts in these genera. More pollination shifts occur in subfamily Crocoideae (ca. 1000 spp.) because the ancestral flower includes tepals united basally into a floral tube and bilateral symmetry. With 16 derived pollination mechanisms described for this family in sub-Saharan Africa it is obvious that phylogenetic constraint is sufficiently flexible to explain the shifts in pollination mode