Reproductive biology of the genus Androcymbium (Colchicaceae) in western southern Africa

Abstract

We characterized reproductive biology traits in 32 populations belonging to 17 western southern African taxa of the genus Androcymbium (Colchicaceae) using artificial pollination experiments conducted under homogeneous environmental conditions in a greenhouse. The species surveyed displayed differences in phenological periods between emergence, flowering and senescence. We observed three types of vegetative reproduction that give rise to (1) globose corms, (2) compressed corms, and (3) a dichotomous underground networking of corms that, unlike (1) and (2), entails the elongation of the stem. Seed germination was low in most of the populations. The artificial pollination experiments allowed us to recognize three reproductive systems: self-incompatible, preferentially self-incompatible and self-compatible. In most cases, the reproductive system inferred from the artificial pollination experiments disagreed with the classification according to the P/O ratio. The variability observed in nectar characteristics (odour, amount and moment of the day of nectar production) suggests different pollinators for the taxa surveyed. Based on these data, we inferred three reproductive strategies in Androcymbium that assure both species' survival and the maintenance of levels of genetic variability: (1) preferential selfincompatibility associated with morphological traits that favour the attraction of pollinators; (2) preferential self-incompatibility with high levels of vegetative reproduction; and (3) self-compatibility with high levels of seed production.