The chemical ecology of multispecies interactions: how secondary metabolites mediate pollination and herbivory

多物种相互作用的化学生态学：次生代谢物如何介导授粉和食草

• 批准号: RGPIN-2014-06496
• 负责人: Manson, Jessamyn
• 金额: $ 1.42万
• 依托单位: University of Alberta
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2016
• 资助国家: 加拿大
• 起止时间: 2016-01-01 至 2017-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=612261
• 关键词: chemical; ecology; multispecies; interactions; how

Flowering plants produce nectar to attract pollinators. It is therefore unusual that floral nectar frequently contains secondary metabolites, noxious compounds commonly used to defend plants from herbivores. Hypotheses to explain this so-called “toxic” nectar include protecting flowers from nectar robbing animals, encouraging specialized pollination and preventing microbial growth, but nectar secondary metabolites may also be an unintended consequence of chemical defenses in leaves. Nectar secondary metabolites can have significant effects on pollinator health and behaviour. Animals can avoid visiting flowers with “toxic” nectar or may reduce the number of visits or length of time spent per flower. Consuming nectar secondary metabolites can reduce nutrient assimilation and mobility in pollinators and, in some cases, cause death. Given their effects on pollinators, nectar secondary metabolites are predicted to have significant consequences for pollination and plant reproduction, however this has rarely been examined. My proposed research will address the role of nectar chemistry in mediating plant-pollinator interactions and plant reproductive success. Research will focus on milkweeds (Asclepias spp), which have become a model system for studying plant chemical ecology. Milkweeds produce secondary metabolites called cardenolides that can be very toxic to herbivores. These compounds are also be found in milkweed nectar, but their effects on pollinators and pollination are currently unknown. The goal of my research program will be to determine whether nectar cardenolides in milkweeds incur an ecological cost to plants by deterring pollinators, inhibiting pollination and reducing seed production. To investigate the effects of milkweed nectar chemistry on pollination, my research group will use a combination of laboratory assays, greenhouse trials and manipulative field experiments. First, we address how nectar cardenolides alter the foraging behaviour of bumble bees, common pollinators of milkweeds. In the laboratory, we will test how nectar cardenolides affect pollinator preference and whether variation in nectar sugar concentration or nectar volume influence this preference. We will then examine the direct effects of herbivory on nectar chemistry and pollination using monarch caterpillars. We will allow caterpillars to feed on milkweed plants in the greenhouse and will subsequently release bumble bee workers to visit milkweed flowers, looking for changes in nectar chemistry, pollinator behaviour and pollination success due to herbivory. Finally, we will plant milkweeds in field plots and look at how herbivory by caterpillars affects wild pollinator behaviour and pollination. We will use molecular techniques to track paternity of seeds within these plots to assess whether the effects of herbivory on nectar chemistry change how genes move within the plant population. Pollination is essential to both wild and agricultural ecosystems and understanding the relationships between plants and pollinators is critical to preserving ecosystem function and biodiversity. Taken together, these experiments will provide new insight into the role of nectar chemistry in structuring complex multispecies interactions in terrestrial ecosystems.

开花植物产生花蜜来吸引传粉者。因此，花的花蜜经常含有次生代谢物是不寻常的，这些有毒化合物通常用于保护植物免受草食动物的侵害。解释这种所谓的“有毒”花蜜的假设包括保护花朵免受花蜜掠夺动物的侵害，鼓励专门授粉和防止微生物生长，但花蜜次级代谢产物也可能是叶子中化学防御的意外结果。花蜜次生代谢产物对传粉者的健康和行为有重要影响。动物可以避免访问具有“有毒”花蜜的花朵，或者可以减少访问每朵花的次数或时间长度。消耗花蜜的次级代谢产物会降低传粉者的营养同化和流动性，在某些情况下，会导致死亡。考虑到它们对传粉者的影响，花蜜次生代谢产物被预测对授粉和植物繁殖具有重要影响，然而这很少被研究。 我提议的研究将解决花蜜化学在介导植物-传粉者相互作用和植物繁殖成功中的作用。研究将侧重于马利筋（马利筋属），它已成为研究植物化学生态学的模式系统。马利筋产生的次级代谢产物称为强心内酯，对食草动物有很大的毒性。这些化合物也存在于马利筋花蜜中，但它们对传粉者和授粉的影响目前尚不清楚。我的研究计划的目标将是确定乳草中的花蜜Cardenolides是否会通过阻止传粉者，抑制授粉和减少种子产量而对植物造成生态成本。 为了研究马利筋花蜜化学对授粉的影响，我的研究小组将结合实验室测定、温室试验和人工田间试验。首先，我们解决如何花蜜cardenolides改变觅食行为的熊蜂，常见的授粉马利筋。在实验室中，我们将测试花蜜cardenolides如何影响传粉者的偏好，以及花蜜糖浓度或花蜜体积的变化是否会影响这种偏好。然后，我们将研究食草动物花蜜化学和授粉使用君主毛虫的直接影响。我们将允许毛毛虫在温室中以马利筋植物为食，随后将释放熊蜂工人访问马利筋花，寻找花蜜化学，传粉者行为和传粉成功的变化，由于食草动物。最后，我们将在田间种植马利筋，并研究毛虫的植食性如何影响野生传粉者的行为和授粉。我们将使用分子技术来追踪这些地块内种子的亲子关系，以评估食草动物对花蜜化学的影响是否会改变基因在植物种群内的移动方式。 传粉对野生和农业生态系统都至关重要，了解植物和传粉者之间的关系对于保护生态系统功能和生物多样性至关重要。两者合计，这些实验将提供新的见解花蜜化学结构复杂的多物种相互作用在陆地生态系统中的作用。