The long spur of Impatiens macrovexilla may reflect adaptation to diurnal hawkmoth pollinators despite diverse floral visitors
The long spur of Impatiens macrovexilla may reflect adaptation to diurnal hawkmoth pollinators despite diverse floral visitors
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凤仙花的长刺可能反映了对昼间天蛾传粉媒介的适应，尽管花卉访客多种多样
作者：
Ya-Fei Tang;Ye Fang;Chang-Qiu Liu;Qing-Biao Lu;Xing-Hua Hu
许多热带和亚热带凤仙花具有明显的长而窄的距，在该属的花进化研究中被归类为蝴蝶传粉综合征。然而，这与之前的一些研究相矛盾，这些研究记录了大量的鹰蛾访客，而不是蝴蝶。在本研究中，我们探讨了凤仙花的授粉生态，凤仙花是亚洲的一种长期受刺激的物种。我们调查了一系列花卉性状，测试了不同访花客的繁育系统和对生殖成功的贡献，观察了访花客，并比较了采蜜访花者的短枝长度和喙长度。花的特征不能明显地与某一类长鼻虫联系在一起。结果表明，该物种在不同地点、不同年份都有大型采蜜蜜蜂、昼夜鹰蛾、小型采粉昆虫和罕见的蝴蝶到访。授粉处理表明，大叶黄花是自交亲和的(自交不亲和指数=0.02)，但完全依靠访花授粉。一项排除了天蛾，但允许收集花粉的昆虫造访花朵的处理表明，白天的天蛾对该物种的繁殖成功做出了很大贡献，但收集花粉的昆虫充当了花粉窃贼的角色。大型蜜蜂在造访花朵时牢牢地接触花药和柱头，因此很可能也是传粉者。大型蜜蜂的鼻子长度不到大黄蜂刺状物的一半，这表明它们只能接触到聚集在刺状物嘴附近的花蜜。然而，鹰蛾可以接触到大部分或所有的花蜜，因为它们的杀虫剂与花刺的长度相匹配。因此，长长的花蜜刺可能反映了对白天天蛾的适应。我们的研究使用了来自多条调查路线的证据，首次证实了凤仙花中白天的天蛾作为传粉者的作用。
Many tropical and subtropical Impatiens species possess conspicuously long and narrow spurs and have been assigned to the butterfly pollination syndrome in investigations of floral evolution of this genus. However, this contradicts some previous studies documenting abundant hawkmoth visitors rather than butterflies. In this study, we explored the pollination ecology of Impatiens macrovexilla, a long-spurred species in Asia. We investigated a series of floral traits, tested the breeding system and contributions of different floral visitors to reproductive success, observed floral visitors and compared the spur length with the proboscis length of the nectar-collecting floral visitors. I. macrovexilla shows floral traits that cannot clearly be associated with a certain group of long-proboscid insects. Results showed that the species was visited by large nectar-collecting bees, diurnal hawkmoths, small pollen-collecting insects and rarely butterflies at different sites and in different years. Pollination treatments indicated that I. macrovexilla is self-compatible (Self-Incompatibility Index = 0.02) but completely relies on floral visitors for pollination. A treatment which excluded hawkmoths but permitted pollen-collecting insects to visit flowers revealed that diurnal hawkmoths contributed considerably to reproductive success of this species but that pollen-collecting insects acted as pollen thieves. Large bees firmly contacted anthers and stigmas when visiting flowers so probably also act as pollinators. The proboscises of large bees were shorter than half of the spur of I. macrovexilla in length, suggesting that they could only access the nectar accumulated near the mouth of the spur. However, hawkmoths can access most or all of the nectar because their proboscides match the length of the floral spur. Thus, the long nectar spur presumably reflects adaptation to diurnal hawkmoths. Using evidence from multiple lines of investigation, our study is the first to confirm the role of diurnal hawkmoths as pollinators in Impatiens.