POLLINATORS, INCLUDING BUMBLE BEES, ARE VITAL FOR MAINTAINING CROP PRODUCTION AND NATURAL BIODIVERSITY, AND ARE CURRENTLY EXPERIENCING NUMEROUS STRESSORS. ONE MAJOR STRESSOR FACED BY POLLINATORS TODAY IS CLIMATE CHANGE. SPECIFICALLY, INCREASING CARBON DIOXIDE (CO2) LEVELS AS ELEVATED CO2 CAN ALTER PLANT PHENOLOGY AND PHYSIOLOGY. CHANGES TO PLANTS IN RESPONSE TO ELEVATED CO2 CAN INCLUDE CHANGES TO FLORAL RESOURCES. FOR EXAMPLE, ELEVATED CO2 CAN LEAD TO CHANGES IN POLLEN OR NECTAR NUTRITIONAL QUALITY AS SOME PLANTS HAVE A LOWER POLLEN PROTEIN CONTENT WHEN GROWN IN ELEVATED CO2 CONDITIONS. AS MANY POLLINATORS, AND BEES SPECIFICALLY, RELY ON POLLEN AS THEIR PRIMARY SOURCE OF PROTEIN, A DECREASE IN POLLEN PROTEIN CONTENT COULD HAVE SUBSTANTIAL NEGATIVE CONSEQUENCES FOR BEE NUTRITION AND OVERALL HEALTH BUT THESE EFFECTS ARE NOT YET WELL UNDERSTOOD.IN THIS RESEARCH, I WILL ADDRESS KEY KNOWLEDGE GAPS IN HOW ELEVATED CO2 ALTERS THE CHEMISTRY AND NUTRITIONAL VALUE OF THE FLORAL RESOURCES (POLLEN AND NECTAR) THAT POLLINATORS RELY ON FOR FOOD AND HOW CHANGES TO FLORAL RESOURCES MAY ALTER POLLINATOR FORAGING BEHAVIOR OR PHYSIOLOGY. SPECIFICALLY, I WILL CHARACTERIZE THE EFFECT OF ELEVATED CO2 LEVELS ON NECTAR AND POLLEN PRODUCTION (QUANTITY) AND CHEMISTRY IN SIX FLORAL SPECIES ESSENTIAL FOR POLLINATORS. THESE SIX PLANT SPECIES REPRESENT MULTIPLE LIFE HISTORY TRAITS AND SPAN A RANGE OF DIFFERENT PLANT FAMILIES. TOGETHER THESE PLANTS INCLUDE A RANGE OF BOTH FUNCTIONAL AND PHYLOGENETIC DIVERSITY AND WILL ALLOW US TO EVALUATE POTENTIALS TRENDS ACROSS PLANT FAMILIES OR FUNCTIONAL GROUPS IN RESPONSE TO ELEVATED CO2 GROWING CONDITIONS. AFTER EVALUATING HOW FLOWERING PLANTS RESPOND TO ELEVATED CO2 CONDITIONS, I WILL THEN INVESTIGATE HOW FLORAL RESOURCES GROWN UNDER ELEVATED CO2 MAY AFFECT POLLINATORS. TO DO SO, I WILL USE THE COMMON EASTERN BUMBLE BEE (BOMBUS IMPATIENS) AS A MODEL SPECIES AS IT IS A CRITICAL POLLINATOR OF BOTH WILD AND CROP PLANTS IN NORTH AMERICA. I WILL EVALUATE CHANGES TO FORAGING BEHAVIOR OR FLORAL PREFERENCES, BEE PHYSIOLOGY, AND COLONY GROWTH OF THE COMMON EASTERN BUMBLE BEE WHEN PROVIDED FLORAL DIETS GROWN IN BOTH AMBIENT AND ELEVATED CO2 CONDITIONS.THE PROPOSED RESEARCH WILL ADDRESS THREE MAIN QUESTIONS: (OBJECTIVE 1) HOW DOES THE PROJECTED INCREASE IN ATMOSPHERIC CO2 AFFECT THE NUTRITIONAL VALUE OF FLORAL RESOURCES? (OBJECTIVE 2) DOES BUMBLE BEE FORAGING BEHAVIOR OR FLORAL PREFERENCES CHANGE WHEN FLORAL RESOURCES ARE GROWN UNDER ELEVATED CO2? (OBJECTIVE 3) WHAT ARE THE IMPACTS OF ELEVATED CO2 POLLEN RESOURCES ON BUMBLE BEE QUEEN OVERWINTERING, SURVIVAL AND COLONY GROWTH?THE PROPOSED WORK WILL GENERATE FOUNDATIONAL KNOWLEDGE ON HOW PROJECTED INCREASES IN ATMOSPHERIC CO2 WILL IMPACT BEE BIOLOGY AND MAY IMPACT FUTURE POLLINATION SERVICES TO BOTH WILD AND AGRICULTURAL CROP PLANTS. DATA GENERATED BY THIS PROJECT WILL BE ESSENTIAL IN MAKING MANAGEMENT AND CONSERVATION DECISIONS TO SECURE THE POLLINATION SERVICES AND ENSURE FUTURE FOOD SECURITY FORTHE HUMAN POPULATION.