The effectiveness of pollinators and their foraging behavior on Neustanthus phaseoloides (Fabaceae)

Insect pollination is critical for the reproduction of crops and wild plants, yet the efficiency of pollinators varies widely across species. Hence, it is essential to study the visitation behavior and pollination effectiveness of the floral visitors. Neustanthus phaseoloides is an agro-ecologically and medicinally important plant occurring in Tripura, Northeast India. We selected it for the present investigation as its distinct floral morphology might impact the pollinator visitation behaviors and subsequent pollination success. A total of 12 insect foragers visited the flowers of N. phaseoloides. Among them, 10 generalist pollinators were observed depositing conspecific pollen along with some amount of heterospecific pollen grains on the stigma. Although the pollen deposition efficiency varied significantly among pollinator species, the bees were the most effective in pollen deposition and subsequent reproductive outputs. All pollinators contributed to the fruit and seed production at varying degrees, indicating their effectiveness in reproductive success. The mating system studies indicated that the species was self-compatible and dependent on pollinators for increased reproductive success. Furthermore, some degree of pollination deficit was detected in our study population, suggesting that the increased visitation of effective pollinators might enhance the reproductive outputs. Overall, this first report on the pollination effectiveness of N. phaseoloides will improve our understanding of the reproductive success in a medicinally useful wild plant.