This project seeks to discover how global warming and disease interact to impact bee health and pollination services. More specifically, the major goals of this research are to:Investigate how heat stress affects pathogen resistance and pathogen transmission for the common eastern bumblebee (Bombus impatiens)Assess how heat stress and infection interact to affect pollination services provided by the common eastern bumblebee for growing tomatoes in greenhouses.These research goals are crucial because the common eastern bumblebee is managed for pollinating tomatoes in greenhouses - among other important agricultural applications - and because management practices will benefit from predictions about how these pollinators will respond to interacting stressors in a changing world. To accomplish these goals, this project will investigate the mechanistic connections between individual physiology and community-level behaviors in field-realistic scenarios. The research will measure how the thermal environment and disease interact to impact individual bee health, pathogen transmission within colonies, and pollination services for tomatoes in greenhouses.The objectives of this research assess basic eco-physiological questions about bee health and measurable crop pollination services in field-realistic scenarios for an agriculturally important crop that utilizes bumblebee colonies for pollination in greenhouses.Objective 1. Determine whether infection affects the thermal tolerance of individuals, and whether the thermal environment affects individual pathogen resistance.I will inoculate individual bees with a gut pathogen (Crithidia bombi), subject them to heat stress (thermal environments from 23 C to 40 C in 4 C increments) then measure survivorship and pathogen infection intensity. I will compare these results to measurements from control cases (uninfected bees subjected to the same heat stress treatments).Objective 2. Determine whether the thermal environment affects the rate at which pathogens are transmitted within colonies, and whether the thermal environment affects offspring production for both infected and uninfected colonies.I will introduce one infected individual into replicated microcolonies (9 healthy bees in each microcolony), subject each microcolony to heat stress (thermal environments from 23 C to 40 C in 4 C increments), then (after 14 days) measure pathogen transmission (the percentage of uninfected bees that have acquired infection), and colony reproduction success (brood temperature, egg number, and larval mass). I will compare these results to measurements from control cases (reproductive success for uninfected colonies subjected to the same heat stress treatments).Objective 3. Determine whether pollinator pathogen infection and heat stress (for both plants and pollinators) affect pollination services for tomatoes in greenhouses.I will grow tomatoes in greenhouses controlled to simulate various heat stress scenarios, introduce infected microcolonies to pollinate the tomatoes, then measure fruit set and quality (fruit mass and seed set). I will compare the results to measurements from control cases (tomatoes pollinated by uninfected bees under the same heat stress scenarios).Tomato plants are especially sensitive to heat stress; therefore I will collaborate with my advisory committee (commercial high tunnel tomato growers and University of Massachusetts vegetable crop extension specialists) to identify a realistic range of heat stress scenarios.Understanding the ways that heat stress and disease interact to impact pollination services is important because global change may introduce synergistic interactions between disease dynamics and plant and pollinator health that shape crop yield. This research is critical for climate adaptation. The results of this research will inform best practices for managing disease transmission among pollinators on farms, to advance sustainable crop production (especially for greenhouse tomatoes), and reduce disease spillover into wild bee populations, despite changing environmental stressors.The objectives of this research assess basic eco-physiological questions about bee health, and measurable crop pollination services in a field-realistic, agriculturally important crop that utilizes managed bumblebee colonies for greenhouse and high tunnel production. Isolating the effects of heat stress on pollinator disease transmission can guide protocols to both optimize agriculturally managed bumblebee health and crop production.