The mechanical fit of the flowers of Crotalaria paniculata Willd. for the pollination success of large-bodied bees

Abstract

The present study investigates the morphology of floral parts adapted towards the mode of pollination by bees in a lesser-known shrub, Crotalaria paniculata Willd of the family Fabaceae. The morphology and orientation of flowers, colour, shape, size and number of each floral part were recorded. The floral odour was assessed qualitatively at various stages of flowers manually and the quantity of nectar produced per flower was also measured. The flowering individuals were regularly monitored to observe the floral visitors and their foraging activity on a series of aged flowers. The performance of each floral visitors like visitation frequency, handling time, relative abundance, activity rate, visitation rate index and visitor activity index was calculated. The flowers of C. paniculata are typical papilionaceous and keel-blossom types that function as floral advertisement and nectar and pollen grains are served as floral rewards. The standard petal serves an advertisement whereas the wing-keel complex acts as a landing platform for floral visitors. The large-bodied bees tend to break the wing-keel complex which facilitates cross-pollination. Xylocopa latipes (Apidae) was observed as the most effective pollinator due to their higher frequency of visits, activity rate, visitation rate index and visitor activity index. Due to the pressure applied by large-bodied bees like Xylocopa latipes by landing on the wing-keel complex, the reproductive parts become exposed and the stigma brushes the pollen load in the body of the visitors and effect cross-pollination. The study concludes that large-bodied bees are effective floral visitors of C. paniculata which effect cross-pollination.