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

这项研究将通过三种途径调查互惠关系是否可以调节营养级联，特别是大黄蜂的寄生虫是否会影响植物种群。首先，理论模型将被用来探索互助者的相互依赖如何改变拮抗者对互助者群体的影响。其次，将进行多地点调查，将大黄蜂寄生的发生率与五种植物的繁殖联系起来，这些植物对大黄蜂授粉的依赖程度不同。这一设计验证了这样一种预测，即对于更依赖大黄蜂的植物，寄生与植物繁殖成功之间将存在更强的负相关。最后，将利用笼子实验研究大黄蜂的行为，以调查寄生对觅食行为和授粉效率的影响，并确定寄生行为的变化是否会影响授粉。互惠，即两个物种之间的生态互动，在其中都受益，正成为生物群落中主要的结构力量。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互利。捕食者和寄生虫有可能对它们的猎物和猎物的互惠伙伴产生负面影响。此外，通过互惠互动形成营养级联的潜力可能会受到合作伙伴相互依赖程度的影响。更广泛的影响包括对博士候选人的培训和对农业的潜在应用。寄生虫对受管理的蜜蜂种群产生了戏剧性的影响，但我们才刚刚开始了解它们如何影响本地传粉者。这项研究将使我们能够更好地了解传粉者的拮抗者，从而帮助我们保存它们对世界经济的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.