DISSERTATION RESEARCH: Mutualisms in trophic cascades: the effects of parasites of bumble bees on pollination

本研究将通过三种方法调查互惠关系是否可以介导营养级联，特别是大黄蜂寄生虫是否可以影响植物种群。首先，将使用理论模型来探讨互惠主义者的相互依赖如何改变拮抗者对互惠主义者群体的影响。其次，将进行多地点调查，将大黄蜂寄生的发生率与对大黄蜂授粉依赖性不同的五种植物的繁殖联系起来。这一设计验证了一个预测，即寄生与更依赖于大黄蜂的植物的繁殖成功率之间存在更强的负相关。最后，通过笼养实验对大黄蜂的行为进行研究，探讨寄生对觅食行为和传粉效率的影响，并确定寄生导致的行为变化是否会影响传粉。共生关系，即两个物种之间互利互惠的生态相互作用，正逐渐被认为是生物群落的主要结构力量。群落生态学中的一个关键概念是营养级联，即捕食者通过对食草动物的影响来影响植物。然而，这一概念从未被明确地应用于互惠关系。捕食者和寄生虫有可能对它们的猎物和猎物的共生伙伴产生负面影响。此外，通过相互作用产生营养级联的可能性可能会受到伴侣相互依赖程度的影响。更广泛的影响包括培养博士候选人和潜在的农业应用。寄生虫对管理的蜜蜂种群产生了巨大的影响，但我们才刚刚开始了解它们是如何影响本地传粉者的。这项研究将有助于更好地了解传粉媒介的拮抗物，从而帮助我们保护它们对世界经济的2000亿美元价值。

This research will investigate whether mutualisms can mediate trophic cascades, and specifically whether parasites of bumblebees can affect plant populations, via three approaches. First, theoretical models will be used to explore how the interreliance of mutualists changes the effects of antagonists on mutualist populations. Second, a multi-site survey will be conducted, correlating incidence of bumble bee parasitism with reproduction of five plant species that vary in their dependence on bumble bees for pollination. This design tests the prediction that there will be stronger negative correlations between parasitism and plant reproductive success for plants that are more dependent on bumble bees. Finally, studies of bumble bee behavior using cage experiments will be used to investigate the impacts of parasitism on foraging behavior and pollination efficiency, and to establish whether changes in behavior due to parasitism can affect pollination. Mutualisms, ecological interactions between two species in which both benefit, are becoming recognized as major structuring forces in biological communities. A key concept in community ecology is that of the trophic cascade, in which predators affect plants through effects on herbivores. However, this concept has never been explicitly applied to mutualisms. Predators and parasites have the potential to negatively affect both their prey and their prey's mutualist partners. Furthermore, the potential for trophic cascades through mutualist interactions will likely be influenced by the degree to which partners rely on each other. Broader impacts include training of a Ph.D. candidate and potential application to agriculture. Parasites have had a dramatic effect on populations of managed honeybees, yet we are only beginning to understand how they can impact native pollinators. This research will enable better understanding of antagonists of pollinators, thus helping us preserve their $200 billion value to the world economy.