Pollination ecology of Rhododendron wardii (Ericaceae), a species native to the southwest mountains of China

To understand the reproductive traits of Rhododendron wardii (Ericaceae), a native shrub evaluated as least concern in the southwest mountains of China, pollination ecology of this species was investigated in a population on Baima Snow Mountain in northwest Yunnan in two years. The results showed that the flower number on each florescence ranged from 2 to 9, with 5-7 flowers per inflorescence as dominance. Flower of R. wardii was characteristics of herkogamy, and could produce nectar reward to animal pollinators. Both autonomous selfing and apomixis did not occur in R. wardii, and partial self-compatibility was identified in this species. Manual outcrossing increased fruit set significantly, indicating pollination limitation of seed production in R. wardii. Emasculation reduced fruit set significantly, indicating the occurrence of pollinator medicated selfing within one flower. Bees, flies, butterflies and beetles were observed to visit R. wardii, but bees and flies were determined as the effective pollinators, although the total visiting frequencies of bees and flies were very low, which could contribute to the pollination limitation of seed production. The results of this study suggest that pollen limitation of seed production resulted from low pollinator visiting frequency could be alleviated by artificial enhancement of plants via increasing potential outcrossing pollen grains, which would be helpful in population regeneration of R. wardii.