J Syst Evol

• Research Articles •    

An altitude-related shift of relative abundance from insect to sunbird pollination in Eleagnus umbellata (Elaeagnaceae)

Hua-Qiang Pi1, Qiu-Mei Quan2, Bo Wu3, Xiao-Wen Lv1, Li-Min Shen4, and Shuang-Quan Huang1*   

  1. 1Institute of Evolution and Ecology, School of Life Sciences, Central China Normal University, Wuhan 430079, China
    2College of Environmental Science and Engineering, China West Normal University, Nanchong 637002, Sichuan, China
    3School of Primary Education, Fuzhou Preschool Education College, Fuzhou 344100, Jiangxi, China
    4Tangjiahe National Nature Reserve, Guangyuan 628000, Sichuan, China
  • Received:2020-09-06 Accepted:2020-09-14

Abstract: The evolution of floral traits has been thought to be influenced by local, effective pollinators. However, little attention has been paid to the possibility that altitudinal variation in floral traits could be mediated by local pollinator functional groups, particularly a shift from bees to birds. Plant size, floral traits, pollinators and their pollination roles were investigated in the spring-flowering shrub Elaeagnus umbellata (Elaeagnaceae) at three altitudes (1160, 1676 and2050 m) in Minshan, Sichuan Province, on the northern rim of the Hengduan Mountains, southwest China. Compared to lower altitudes, higher-altitude plants were smaller but the floral tubes were longer, with a larger volume of nectar of lower sugar concentration but with a greater proportion of sucrose. The visitation frequency of bees decreased with altitude, whereas the sunbirds did the opposite. Birds and bees foraged for nectar but not pollen, and birds deposited more pollen grains per visit relative to bees and least were syrphid flies. Excluding birds decreased seed set at high but not at mid- or low altitude. Our study of E. umbellata revealed an association between altitudinal variation in floral traits and a change in the relative abundance of the major pollinators with altitude from majority bees to majority sunbirds. While abiotic factors also tend to vary with altitude and can affect floral traits, nectar properties of ‘pro-bird’ pollination were observed at high altitude.

Key words: altitude, bee, bird, Elaeagnus umbellata, floral traits, nectar, pollination ecotypes, pollinator effectiveness