Social Behavior and the Ecology of Infectious Disease
Access to this document is restricted. Some items have been embargoed at the request of the author, but will be made publicly available after the "No Access Until" date.
During the embargo period, you may request access to the item by clicking the link to the restricted file(s) and completing the request form. If we have contact information for a Cornell author, we will contact the author and request permission to provide access. If we do not have contact information for a Cornell author, or the author denies or does not respond to our inquiry, we will not be able to provide access. For more information, review our policies for restricted content.
Infectious disease is a threat for both human and wildlife health. Social behavior can shape the outcomes of disease, and infectious disease can reciprocally shape the evolution of social behavior. Bumble bees, dominant pollinators in temperate ecosystems, are eusocial and have experienced declines associated with pathogens, but we have a limited understanding of how bumble bee social life affects the ecology of disease in pollinator communities. In this thesis, I investigate the relationship between social behavior and infectious disease in the common eastern bumble bee. In Chapter 1, I experimentally test whether disease is a cost of living in larger groups, finding that when infected with a gut parasite larger colonies experienced reduced survival, growth, and reproduction compared to smaller colonies. However, while social behavior can increase the costs of disease, it can also select for cooperative defenses that may counteract these costs. In Chapters 2 and 3 I explore the social defenses used by bumble bees against this gut parasite. First, in Chapter 2, I described a novel element of wild bumble bee nest architecture, a feces-filled secondary cavity, or “outhouse,” through field observations of wild colonies in western Alaska. I also observed a fecally-transmitted gut parasite in this region, suggesting that this architecture could serve a hygienic function. Then in Chapter 3 I test this hypothesis with manipulative laboratory experiments, finding that bumble bee colonies modify their nests to create the “outhouse” architecture and that this enables hygienic waste removal behaviors, thereby slowing pathogen transmission, accelerating growth, and increasing reproduction. These results extend our understanding of the consequences of social behavior on the ecology of infectious disease in plant-pollinator-pathogen communities, and suggest an effective and cost-effective solution for reducing pathogen transmission in managed pollinators. By better understanding the social lives of bees, we will be able to improve predictions of the outcomes of epidemics and develop more effective strategies for their management, in support of pollinator conservation.