Pollen morphology of Adenandra (Rutaceae : Diosminae) and its taxonomic implications

The pollen morphology of Adenandra Willd. (Rutaceae: Diosminae) was investi gated to determine its taxonomic significance. Pollen of 27 of the 30 infra generic taxa (representing 16 of the 18 species) was investigated by LM, SE M and TEM. Adenandra differs from all other Diosminae in having 4-colporate rather than 3-colporate pollen grains. This supports the alleged monophyle tic status of the genus. Exine morphology and structure, however, is extrem ely diverse considering the size of the genus, with eight distinct pollen t ypes and four subtypes being discerned. In some members the grains have uni form macroreticulate, striate or striato-reliculate sculpturing, whereas in others the poles have striate, striato-reticulate or reticulate-perforate sculpturing with various types of reticulate or rugulate sculpturing at the mesocolpia. Taxonomic groupings revealed by the pollen characters suggest relationships between taxa that were not previously apparent. It is suggest ed that evolutionary diversification among species of Adenandra is often mo re strikingly reflected by pollen morphology than by macromorphology, hence the eurypalynous state of the genus.