Reproductive biology ofDiscaria toumatou(Rhamnaceae)

Abstract

Abstract The flowers of Discaria toumatou (Rhamnaceae) at Cass, Canterbury, are visited by a wide range of nectar and pollen collecting insects. In flowers bagged to exclude insects, only cross-pollinated flowers set fruit, with no fruit set in self-pollinated or control flowers. Fruit set in flowers exposed to insect visits was 6.7% in control flowers and 3.3% in self-pollinated flowers, but increased to 15% in cross-pollinated flowers. Pollen transfer between plants is clearly needed for fruit production but insects do not transfer sufficient amounts of pollen for full fruit set. However, low fruit set even in cross-pollinated flowers and no fruit set on many individual plants indicate that other factors besides pollinator activity limit fruit production. The ability of the unbroken fruit to float in sea water and the self-infertility suggest that a fruit containing more than one seed is the unit of long-distance dispersal across oceans for the ancestor of this species.