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关键模式之一。尽管花香被认为可调控传粉者行为，但目前学界对其在野外条件下对传粉者吸引及访花行为的影响仍知之甚少。
我们利用野生天蛾的野外实验与无经验天蛾的室内实验，探究了吲哚（indole）——一种由细叶山字草（Ipomopsis tenuituba）而非其近缘种聚合山字草（I. aggregata）释放的挥发性物质——单独存在及与花色差异结合时，对天蛾的花朵吸引行为与探花行为的影响。
实验结果表明，吲哚可将野生天蛾吸引至花朵处，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吸引效率，但可促使更多被吸引的天蛾开展探花行为。
因此，天蛾需依次依赖花香与高视觉对比度的信号，才能在黄昏时刻前往花朵取食。天蛾对吲哚花香花朵的偏好是先天的，但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削弱。
这种依赖环境的行为模式，有助于解释为何这些山字草属（Ipomopsis）物种的杂交程度存在地理变异，同时也有望解释其他天蛾传粉植物系统中杂交桥的形成。