生物多样性 ›› 2019, Vol. 27 ›› Issue (4): 373-379.DOI: 10.17520/biods.2019003

• 研究报告: 植物多样性 • 上一篇    下一篇

木棉黄花个体的适应意义

向文倩,任明迅()   

  1. 海南大学生态与环境学院环南海陆域生物多样性研究中心, 海口 570228
  • 收稿日期:2019-01-07 接受日期:2019-05-04 出版日期:2019-04-20 发布日期:2019-06-05
  • 通讯作者: 任明迅
  • 基金资助:
    海南省创新团队项目(2018CXTD334);国家自然科学基金(31670230)

Adaptive significance of yellow flowered Bombax ceiba (Malvaceae)

Xiang Wenqian,Ren Mingxun()   

  1. Center for Terrestrial Biodiversity of the South China Sea, College of Ecology and Environment, Hainan University, Haikou 570228
  • Received:2019-01-07 Accepted:2019-05-04 Online:2019-04-20 Published:2019-06-05
  • Contact: Ren Mingxun

摘要:

木棉(Bombax ceiba)花大、红色, 多为鸟媒传粉, 但也存在频率极低的黄花个体, 有蜜蜂访花。本文对比研究了海南岛木棉红花、黄花的花部特征及传粉过程, 以解释黄花个体的适应意义。木棉两种花色表型的花蜜组分(葡萄糖和果糖)及挥发性物质(烷烃类、酯类、酚类等)没有显著差异, 但黄花花瓣的反射波长范围均在鸟类与蜜蜂视觉范围内, 可同时吸引鸟和蜜蜂。木棉黄花的雌雄异熟程度较小(花粉活性时期与柱头可受期重叠较大), 可在传粉媒介访花次数有限的情况下同时输出或接受花粉。另一方面, 黄花有着更大程度的柱头探出式雌雄异位, 降低了较小程度雌雄异熟可能导致的自交与雌雄功能干扰。木棉存在明显的花粉限制, 且黄花的坐果率(1.08 ± 0.56)%显著低于红花(3.27 ± 0.93)%。我们推测, 黄花个体可能通过增加木棉访花者类群多样性、降低雌雄异熟程度而提高了木棉的繁殖成功率, 也通过吸引蜜蜂而降低了蜜蜂对红花鸟媒传粉的干扰。

关键词: 鸟媒传粉, 性别干扰, 异交授粉, 雌雄异熟, 雌雄异位

Abstract:

Bombax ceiba is a tall tree species with predominantly red flowers and is normally pollinated by birds. In some populations, a yellow flowered variety occurs. Honeybees frequently visit these uncommon yellow flowers but how this adaptation affects the life history of this variant remains unexplored. In the present study, floral syndrome and pollination mechanism of yellow flowers were compared with red flowers of B. ceiba populations on Hainan Island, southern China. The results showed that main nectar components of two floral phenotypes are both glucose and fructose dominated, and the volatile chemicals are mainly alkanes, esters, phenols and acids with no significant difference between the two phenotypes. The relative spectral reflectance showed that both birds and honeybees could detect the yellow flowers, suggesting visitation by honeybees can compensate for times when bird visitation is low. Compared with red flowers, yellow flower had a lower degree of dichogamy, which might increase selfing possibilities and provide reproduction assurance when red flowers receive low bird visitation. Interestingly, yellow flowers had a relatively higher degree of herkogamy, i.e. stigmas are much higher than anthers when compared to the red flowers. Greater herkogamy in yellow flowers may reflect an adaptation to decreased dichogamy, avoiding autonomous selfing and interference between female and male organs. Fruit set of the yellow phenotype (1.08 ± 0.56)% was lower than that of red phenotype (3.27 ± 0.93)%, suggesting pollen-limitation in B. ceiba. We propose that yellow flowers, with greater herkogamy but lower dichogamy, promote pollination via attracting diverse pollinators and protect red flowers from disturbance of honeybees.

Key words: bird-pollination, sexual interference, reproductive assurance, dichogamy, herkogamy