Data from: Context-dependent reproductive isolation mediated by floral scent and color

Reproductive isolation due to pollinator behavior is considered a key mode of speciation in flowering plants. Although floral scent is thought to mediate pollinator behavior, little is known about its effects on pollinator attraction and floral visitation in the wild. We used field experiments with wild hawkmoths and laboratory experiments with naïve hawkmoths to investigate attraction to and probing of flowers in response to indole, a volatile emitted by Ipomopsis tenuituba but not its close relative I. aggregata, both alone and in combination with floral color differences. We demonstrated that indole attracts wild hawkmoths to flowers, but has little effect on the rate at which those attracted moths probe flowers. In contrast, white flower color did not influence hawkmoth attraction in the field, but caused more attracted moths to probe flowers. Thus the moths require both scent and high visual contrast, in that order, to feed at flowers at dusk. Their preference for indole-scented flowers is innate, but species-specific preference is mitigated by previous experience and plant spatial patterning. This context-dependent behavior helps explain why these Ipomopsis species show geographical variation in the extent of hybridization and may potentially explain formation of hybrid bridges in other systems of hawkmoth-pollinated plants.

由传粉者行为介导的生殖隔离，被认为是显花植物物种形成的核心模式之一。尽管学界普遍认为花香可调控传粉者行为，但目前对其在自然生境中对传粉者吸引及访花行为的影响仍知之甚少。本研究通过针对野生天蛾的野外实验，以及针对无经验天蛾的室内受控实验，探究了吲哚（indole）——一种由细叶山福禄考（Ipomopsis tenuituba）释放，而其近缘种聚合山福禄考（I. aggregata）不产生的挥发性次生代谢物——单独存在及与花色差异组合存在时，天蛾对花的定向吸引反应与探花行为。实验结果表明，吲哚可将野生天蛾吸引至花株，但对已被吸引的天蛾的探花速率几乎无影响。与之相反，白色花色在野外并未影响天蛾的整体吸引率，却能促使更多被吸引的天蛾发起探花行为。因此，天蛾需依次依赖花香信号与高视觉对比度信号，才能在黄昏时段于花上取食花蜜。天蛾对携带吲哚花香的花的偏好是先天固有，但这种物种特异性偏好会因过往取食经历与植物空间分布格局而被弱化。这种依赖于环境背景的行为模式，不仅有助于解释上述山福禄考属物种的杂交程度存在地理变异的原因，同时也有望为阐释其他天蛾传粉植物系统中杂交桥的形成机制提供理论参考。