Paudel Babu Ram, Shrestha Mani, Dyer Adrian G, Li Qing-Jun
Key laboratory of Tropical Forest Ecology, Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences, Yunnan, China.
University of Chinese Academy of Sciences, Beijing, China.
PLoS One. 2017 Jul 19;12(7):e0180460. doi: 10.1371/journal.pone.0180460. eCollection 2017.
The Himalayan endemic alpine genus Roscoea, like other members of ginger family, exhibits the combination of floral traits that would fit pollination by long distant foragers such as bees, birds or flies. We studied the pollination biology of Roscoea alpina, observed potential floral visitors and determined their foraging behaviour, visitation frequency and pollination efficiency, to seek evidence in support of the pollination syndrome hypothesis. We also measured the floral spectra of R. alpina flowers to evaluate if signals fit with the currently known framework for observed floral visitors. We found that R. alpina have autonomous selfing and pollinator-mediated crossing, but lack apomixis. We observed that a beetle (Mylabris sp.), and a moth (Macroglossum nycteris) visit the flowers of R. alpina for pollen and nectar feeding respectively. Our field observations, the stigmatic pollen count and fruit set data indicated that the visit by the beetle was legitimate, while that of the moth was illegitimate. Emasculated flowers visited by beetles set as many fruits and seeds/fruit as auto-selfed and naturally pollinated flowers, while emasculated flowers excluded from beetle visits did not set fruit and seed; indicating that a single visit of a beetle to the flowers of R. alpina can facilitate pollination. We found that flower spectral signal of R. alpina does not fit typical spectra previously reported for beetle or bee-visited flowers. Our results suggest that, to ensure reproductive success in alpine habitat, R. alpina has evolved autonomous selfing as a predominant mode of reproduction, while beetle pollination would promote genetic diversity of this plant species. The visitation of beetles to the flowers of R. alpina, despite floral signal mismatch with the classically associated beetle vision, suggests that a different visual processing may operate in this plant-pollinator interaction at high altitudes.
喜马拉雅地区特有的高山姜花属植物Roscoea，与姜科的其他成员一样，具有一些花部特征组合，这些特征适合由蜜蜂、鸟类或苍蝇等长距离觅食者进行授粉。我们研究了高山姜花（Roscoea alpina）的传粉生物学，观察了潜在的访花者，并确定了它们的觅食行为、访花频率和授粉效率，以寻找支持授粉综合征假说的证据。我们还测量了高山姜花花的光谱，以评估其信号是否符合目前已知的访花者观察框架。我们发现高山姜花具有自动自花授粉和传粉者介导的异花授粉，但缺乏无融合生殖。我们观察到一种甲虫（斑芫菁属，Mylabris sp.）和一种蛾类（大长喙天蛾，Macroglossum nycteris）分别访问高山姜花的花朵以获取花粉和花蜜。我们的野外观察、柱头花粉计数和结实数据表明，甲虫的访问是有效的，而蛾类的访问是无效的。被甲虫访问的去雄花结出的果实数量以及每个果实中的种子数量与自动自花授粉和自然授粉的花相同，而被排除在甲虫访问之外的去雄花没有结出果实和种子；这表明甲虫单次访问高山姜花的花朵就能促进授粉。我们发现高山姜花的花朵光谱信号与先前报道的甲虫或蜜蜂访问的花朵的典型光谱不匹配。我们的结果表明，为了确保在高山生境中的繁殖成功，高山姜花已经进化出自动自花授粉作为主要的繁殖方式，而甲虫授粉则会促进该植物物种的遗传多样性。尽管花朵信号与经典的甲虫视觉不匹配，但甲虫对高山姜花的访问表明，在这种高海拔的植物 - 传粉者相互作用中可能存在不同的视觉处理方式。
