J Syst Evol ›› 2020, Vol. 58 ›› Issue (2): 182-188.DOI: 10.1111/jse.12487

• Research Articles • Previous Articles     Next Articles

How floral displays affect geitonogamy in an upward foraging bumblebee‐pollinated protandrous plant

Xing-Fu Zhu1*, Ji-Qin Yang2, and Qing-Jun Li3   

  1. 1CAS Key Laboratory of Tropical Forest Ecology, Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences, Mengla 666303, Yunnan, China
    2Gansu Liancheng National Nature Reserve, Yongdeng County, Lanzhou 730333, China
    3Laboratory of Ecology and Evolutionary Biology, Yunnan University, Kunming 650091, China
  • Received:2018-08-08 Accepted:2019-01-25 Online:2019-02-02 Published:2020-03-01

Abstract: Reducing geitonogamy (pollen transfer among flowers within the same plant) has been suggested as a major selective force for plants with multiple flowers. The occurrence of geitonogamy is generally different among flowers within inflorescences; however, no researchers have examined whether plants enlarge their display size without increasing the possibility of geitonogamy by presenting more flowers at positions where they are less likely to be geitonogamously pollinated. We observed that bumblebee pollinators foraged upward within the tower‐shaped inflorescences of protandrous Megacodon stylophorus (C. B. Clarke) Harry Sm. Because M. stylophorus did not strictly bloom bottom‐up, there were substantial frequencies of geitonogamous pollination resulting from upward and horizontal pollen transfer. Although there was a strong correlation between total numbers of flowers plants produced and numbers of flowers presented on single days, proportions of flowers possibly geitonogamously pollinated were weakly correlated with total numbers of flowers. This might have been because plants with more resources enlarged their display size by producing more flowers on lower floors where flowers had a low probability of being geitonogamously pollinated. This study shows that the tower‐shaped inflorescences of M. stylophorus enlarge their size without more cost of geitonogamous mating, suggesting that geitonogamy acts as an important selective agent in the evolution of inflorescence architectures.

Key words: floral display, foraging behavior, geitonogamous pollination, Megacodon stylophorus