Evolution and Chemical Ecology of Buzz-Pollinated Flowers and Pollen-Collecting Bees

蜂鸣授粉花和采花粉蜜蜂的进化和化学生态学

• 批准号: 2115571
• 金额: --
• 依托单位: University of Stirling
• 依托单位国家: 英国
• 项目类别: Studentship
• 财政年份: 2018
• 资助国家: 英国
• 起止时间: 2018 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=studentship-2115571
• 关键词: Evolution; Chemical; Ecology; Buzz; Pollinated

More than 70% of flowering plants are animal-pollinated, with many of these plant species relying mainly on bee pollinators. Bees provide essential ecosystem services in natural systems, and play a significant role in the production of several agricultural crops. However, bee populations have recently been negatively affected by a number of environmental stressors, causing serious concern for their health and capacity to continue providing pollination services.The relationship between flowers and their bee pollinators has been shaped through evolutionary time resulting in, sometimes, complex associations between floral traits and the morphology and behaviour of their visitors. One such case is the evolution of buzz pollination, in which nectar-less flowers with specialised morphologies are pollinated by bees that use vibrations to extract pollen grains (Fig. 1). Puzzlingly, the vibrational behaviour used by bees to extract pollen is present in some (e.g., bumblebees) but not in other species (e.g., honeybees). From the plant perspective, the convergence in floral form in unrelated buzz-pollinated plants is a striking example of convergent evolution. The evolution of buzz pollination is not well understood. Floral morphologies associated with buzz pollination include anthers that "lock" their pollen behind anther walls that remain closed after the flower matures (non-dehiscent), and from which pollen is released only through microscopic apertures or pores (poricidal anthers). Previous work has suggested that such a locking mechanism serves to exclude greedy floral visitors and selects for a subset of pollinators that can unlock this type of anthers, for example by producing high frequency vibrations. Therefore one of the main hypothesis for the evolution of buzz pollination is that it represents the escalating solution of an arms race between pollen-rewarding flowers and pollen-collecting insects. However, few empirical studies to date have addressed this hypothesis. The collection of pollen from buzz-pollinated flowers presents a unique opportunity to understand more generally how bees assess pollen rewards, and area that compared to nectar rewards is poorly developed. Anthers of buzz-pollinated flowers "hide" reward levels behind opaque anthers, and therefore bees cannot visually establish reward level (amount of pollen left in the flower). In order to assess reward level, the bee may thus rely on other clues including pollen removal rates, and potentially, chemical cues such as scent. The role of chemical cues has been well studied in nectar-producing species, but we now very little about the role of chemical cues in pollen-only flowers. Understanding how pollen cues mediate pollinator visitation is not only relevant for the thousands of species with pollen-only flowers, but may also have practical applications to improve the pollination of crops such as tomatoes which possess nectarless, buzz-pollinated flowers. The main aim of this project is to investigate the evolution and chemical ecology of buzz-pollinated flowers and their pollen collecting visitors. Specifically, we will address the following questions: 1. What drives the evolution of buzz pollination?2. How does visitation by inefficient pollinators and pollen thieves affect plant reproduction?3. How do bees assess pollen rewards?4. What is the role of visual vs. chemical cues in mediating pollinator visitation of nectarless, buzz-pollinated flowers?5. How can flowers use these visual and chemical cues to manipulate bee behaviour?Ultimately our goal is to understand at both ecological and evolutionary levels the association, and potentially co-evolution, between pollen-rewarding flowers and their bee pollinators.

超过70%的开花植物是动物授粉的，其中许多植物物种主要依赖蜜蜂授粉。蜜蜂在自然系统中提供基本的生态系统服务，并在几种农作物的生产中发挥重要作用。然而，蜜蜂种群最近受到一些环境压力的负面影响，引起严重关注，他们的健康和能力，继续提供授粉services.The花和蜜蜂授粉者之间的关系已经形成通过进化的时间导致，有时，复杂的关联花的性状和形态和行为的游客。其中一个例子是蜂音授粉的进化，其中具有特殊形态的无花蜜花朵由蜜蜂授粉，蜜蜂使用振动来提取花粉粒（图1）。令人困惑的是，蜜蜂用来提取花粉的振动行为存在于一些（例如，大黄蜂）而不是其它物种（例如，蜜蜂）。从植物的角度来看，在不相关的蜂音传粉植物中，花的形式的趋同是趋同进化的一个引人注目的例子。蜂音传粉的进化还没有被很好地理解。与蜂音授粉相关的花的形态包括将花粉“锁定”在花药壁后的花药，花药壁在花成熟后保持闭合（不开裂），并且花粉仅通过微小的孔或孔隙（孔裂花药）从花药壁释放。以前的工作表明，这种锁定机制可以排除贪婪的花访客，并选择一部分可以解锁这种类型花药的传粉者，例如通过产生高频振动。因此，蜂音传粉进化的一个主要假设是，它代表了奖励花粉的花朵和收集花粉的昆虫之间的军备竞赛的升级解决方案。然而，迄今为止，很少有实证研究已经解决了这一假设。从蜜蜂授粉的花朵中收集花粉提供了一个独特的机会，可以更普遍地了解蜜蜂如何评估花粉奖励，与花蜜奖励相比，这一领域发展得很差。蜜蜂授粉的花的花药“隐藏”在不透明的花药后面的奖励水平，因此蜜蜂不能在视觉上建立奖励水平（留在花中的花粉量）。为了评估奖励水平，蜜蜂可能因此依赖于其他线索，包括花粉去除率，以及潜在的化学线索，如气味。化学信号在产蜜植物中的作用已经得到了很好的研究，但我们现在很少了解化学信号在只产花粉花中的作用。了解花粉线索如何介导传粉者的访问不仅与数千种只有花粉的花朵有关，而且还可能具有实际应用，以改善作物的授粉，如西红柿，这些作物具有无花蜜，嗡嗡授粉的花朵。本计画的主要目的是探讨蜂类传粉花卉及其花粉采集访客的演化与化学生态。具体而言，我们将解决以下问题：1.是什么推动了蜂音授粉的进化？2.低效的传粉者和盗粉者的造访如何影响植物的繁殖？3.蜜蜂如何评估花粉的回报？4.视觉与化学线索在介导传粉者访问无花蜜、蜂音传粉的花朵中的作用是什么？5.花如何利用这些视觉和化学线索来操纵蜜蜂的行为？最终，我们的目标是了解在生态和进化水平的关联，并可能共同进化，花粉奖励花和蜜蜂授粉者之间。