Community Characteristics And Pollination Behaviour Of Bumblebees Affecting Sexual Reproduction Of Pedicularis(Orobanchaceae)

Genus Pedicularis L.(Orobanchaceae) consists of more than700species, and majority of them occur in the northern hemisphere alpine areas. Chinese Himalayan was considered as the central region of origin and modern distribution for the genus. Pedicularis species are famous for substantial floral diversity. Bumblebee is the most common and dominant pollinator for Pedicularis species. Pollination behaviour of bumblebee visiting Pedicularis species is complex and diverse. This study focuses on relations between pollination behaviour and floral traits, and moreover, the relations undergoing different community characteristics such as floral hebivory, simultaneously flowering sympatric plants.We established two experimental groups of Pedicularis gruina individuals with and without floral herbivory in two natural populations during two years. Pollinator behaviour within an individual plants were compared between plants of the two groups as well as female reproductive output. Additionally, experiments including hand supplemental pollination at the level of individual plant and artificial removal flowers were conducted to estimate pollen or resource limitation. Results of pollen supplement and artificial flower removal demonstrated female reproductive success is limited by resource availability occurring simultaneously with florivore-mediated pollinators limitation. Floral herbivores decrease pollination service of plants of P. gruina. However, the loss of fruit set can be partially compensated by higher seed set for plants with floral herbivory. Moreover, the capabilities of compensation will vary at spatial and temporal scales, depending on the activity of pollinators and intensity of floral herbivory.We investigated patterns of pollination interaction between Pedicularis monbeigiana and an associated species, Vicia dichroantha that co-flowering and shared pollinators in alpine meadow over two years. Experimental results show that the flowering phenology of Pedicularis between two patch types is similar, but the floral display size of individual Pedicularis plant within pure patches were larger than those of mixed patches. In both years, the proportion of purple phase flowers per plant in mixed patches was higher than those in pure patches. Bumblebee visitation rates of Pedicularis in mixed patches were higher than those in pure patches. Interspecific pollen transfer was very low in both years, either in dense patches or sparse patches. Our results suggested that existence of coflowering V. dichroantha enhance pollination service of P. monbeigiana by providing richer floral nectar.We examined the pollination behaviour of bumblebees and female reproductive success in P. densispica and P. siphonantha. Pollinator visitation rate for P. densispica was higher than that for P. siphonantha in same area, and pollen deposited in P. densispica was less than those of P. siphonantha by the conspecific bumblebees. Our results suggest that seed production per fruit of P. densispica was suffered from pollination efficiency (stigmatic pollen load); however, fruit yield per individual of P. siphonantha was limited pollinator availability. We therefore suggest that buzz pollination in P. siphonantha acts as a mechanism that improves the chance of cross-pollination upon multiple visits if bumblebee visitation is frequent, whereas infrequent visitation by bumblebees compromise pollen disperal, causing pollinators limitation.In a two-year study project, We tested the response of three species of bumblebee to P. densispica and P. gruina inflorescences that were previously visited by conspecifics or heterospecifics, or inflorescences that had never been previously visited (control inflorescences) in natural populations. Our results indicated that three bumblebee species can recognize scent marks by conspecifics or by congeners, and the olfactory cues left on flowers foraged by previous visitors in both louseworts. The rejection rate of bumblebee on flowers foraged by conspecific or congeners decreased as the time lag after the last visit occurred. Our results also suggested that the capability of response to scent marks for bumblebee is dependent on the length of proboscis, handle time per flower and number of flowers foraged per inflorescence. This type of pollination behaviour improves foraging efficiency when collecting resources by reducing the time spent visiting non-rewarding flowers.