Staminal hairs increase pollinator attraction and pollination accuracy in Tradescantia fluminensis (Commelinaceae)

Staminal hairs are the particular appendages of stamens, which may affect pollinator foraging behaviour and pollen transfer. However, experimental evidence of the functions of staminal hairs in pollination remains scarce. Here, we conducted staminal hair manipulation experiments in Tradescantia fluminensis (Commelinaceae) to investigate their effects on visitation and pollen transfer by bees. Our observations revealed that both visitation rates and visit duration of honeybees (Apis cerana) to control flowers were significantly higher than that of hairless flowers. Moreover, removing the staminal hairs significantly decreased pollen deposition by honeybees (A. cerana), but did not affect pollen removal. The staminal hair was similar in length to the stamen and the pistil of T. fluminensis. The staminal hairs provide more footholds for honeybees, and they lay prone on the staminal hairs to collect pollen, which increased the accuracy of pollination through the consistent pollen placement and pick-up on the ventral surface of honeybees. These results showed that the staminal hairs in T. fluminensis may represent an adaptation to attract pollinators and enhance pollination accuracy.