Pollen morphology and biometry of the genus Androcymbium (Colchicaceae) in southern Africa: taxonomic and biogeographic considerations

Abstract

Pollen characters in 16 southern African type specimens of Androcymbium Willd. that represent the three sections into which the genus is presently divided (Androcymbium,  Dregeocymbium and  Erythrostictus), were examined to assess the possibility of sectional characterization based on pollen traits and to explore the relationship between pollen traits and geo­graphic species distribution. Differences in pollen grain size, shape, number of apertures and exine pattern, were observed. Principal Component Analysis, using both qualitative and biometric pollen characters, distinguished four groups of species with four different pollen types. Most of the species have a microreticulate exine pattern with either diaperturate or tria- perturate grains. The remaining species have either a rugulate exine pattern with diaperturate grains, or a rugulate-reticu- late exine pattern with thickened (hypertrophied) muri with diaperturate grains. While section Dregeocymbium can be well delimited by the unique thickened muri. and by a significantly larger grain size, no diagnostic pollen traits were found for sections Androcymbium and  Erythrostictus. Similarly, although the six northern African species exhibit a microreticulate exine pattern, the high variability observed for this trait in their southern African counterparts, does not follow a geographic pattern.