PROTOGYNY, SELF-INCOMPATIBILITY AND POLLINATION IN ANTHOCERCIS-GRACILIS (SOLANACEAE)

The pollination biology of A. gracilis was examined in glasshouse plan ts and natural populations. The species is both protogynous and pre-zy gotically self-sterile (self-incompatible). Protogyny prevents autopol lination (autogamous self-pollination), and self-incompatibility avoid s geitonogamous self-fertilisation. This sequence is essential because prior selfing blocks the style with pollen tubes and prevents subsequ ent outcrossing. Flowers have no discernible daytime odour, the pollen is clumped and not easily shaken from opened anthers, and daytime ins ect visitors are rarely observed in the field. However in long-establi shed populations, mast plants carry one or a few capsules during winte r-spring and seeds per capsule are generally high. Reproduction of nat ural populations involves reliable pollinators of unknown identity, po ssibly small flies, bees or moths lured by a tiny amount of sucrose-ri ch nectar secreted by the hypogynous disc. It is not anomalous that A. gracilis has two devices for preventing self-fertilisation, protogyny and strong self-incompatibility, as both are functional aspects of th e same outcrossing system. This is the first report of self-incompatib ility in the Anthocercideae which is an old and apparently basal linea ge in the Solanaceae.