Sparattosperma leucanthum (Vell.) K. Schum. (Bignoniaceae) is a tree pollinated by carpenter bees, although other floral visitors also explore the nectar or pollen of the flowers without exerting any reproductive benefit. This study focused on aspects of the pollination system and attempted to infer whether the inter-plant spacing found in the sampled area and the number of flowers produced by the tree limited pollination by crossbreeding with S. leucanthum. Reproductive tests were carried out to obtain fruit-flower relationship, counting of the number of seeds per fruit and number of trees in the transects sampled and estimate of the number of flowers per tree. S. leucanthum is self-incompatible and needs floral visitors to carry out pollination, since it only reproduces by crossbreeding. The fruit-flower relationship obtained was 0.0054, indicating a high energy cost attributed to the floral visitors' low efficiency in promoting pollination. The inter-plant distance was relatively shorter than the maximum distance traveled by the carpenter bees, while the trees produced few flowers per inflorescence and in moderate intensity, helping the pollination process by crossbreeding accomplished by the carpenter bees. However, the fruits produced a large number of seeds, allowing a wide proliferation of S. leucanthum in the studied area.
Floral visitors; carpenter bees; self-incompatibility
