** AWARDS ISSUED PRIOR TO JANUARY 20, 2025, WERE FUNDED UNDER PREVIOUS ADMINISTRATIONS AND MAY NOT REFLECT THE PRIORITIES AND POLICIES OF THE CURRENT ADMINISTRATION.** BUMBLE BEES ARE IMPORTANT POLLINATORS IN NATURAL AND AGRICULTURAL ECOSYSTEMS. ONE OF THE MOST UNIQUE, BUT STILL POORLY-UNDERSTOOD, FEATURES OF BUMBLE BEE BIOLOGY IS THE HIGH LEVEL OF SIZE VARIATION OBSERVED AMONG WORKERS IN NESTS. WORKER BODY SIZE INFLUENCES COLONY FUNCTION AND ALSO HAS BROADER CONSEQUENCES FOR PLANT POLLINATION. YET, THERE MANY UNRESOLVED QUESTIONS ABOUT WORKER SIZE, INCLUDING ABOUT HOW IT IS GENERATED, ITS RELATIONSHIP TO COLONY FITNESS, AND HOW IT IS BEING IMPACTED BY GLOBAL CHANGE. THIS PROJECT FOCUSES ON THESE ASPECTS OF WORKER BODY SIZE VARIATION, AND INCLUDES LAB WORK WITH THE MANAGED SPECIES BOMBUS IMPATIENS THAT COMBINES THERMAL IMAGING AND VIDEO OBSERVATION TO STUDY HOW BROOD FEEDING AND INCUBATION INTERACT TO SHAPE SIZE. THE PROJECT ALSO USES A SEMI-FIELD EXPERIMENT (WITH B. VOSNESENSKII) TO STUDY HOW LANDSCAPE CHARACTERISTICS (WILDFIRE AND THE PRESENCE OF HONEY BEES) AND FOOD RESOURCE ACQUISITION INFLUENCE SIZE VARIATION WITHIN NESTS, COUPLED WITH A SIMILAR BUT MORE CONTROLLED EXPERIMENT IN B. IMPATIENS. WORK WITH WILD, FREE-FORAGING BUMBLE BEES (AND LAB-REARED COLONIES) IN CALIFORNIA AND ALASKA WILL EXAMINE RELATIONSHIPS BETWEEN LANDSCAPE CHARACTERISTICS, BODY SIZE, AND PLANT POLLINATION, INCLUDING IN APPLE, A GROWING CROP SYSTEM IN ALASKA. TOGETHER, THIS WORK WILL SHED NEW LIGHT ON THE FACTORS THAT IMPACT BUMBLE BEE BODY SIZE AND HOW THIS MIGHT BE ALTERING POLLINATION OUTCOMES, INCLUDING FOR A SET OF ECONOMICALLY AND ECOLOGICALLY IMPORTANT PLANT SPECIES. ?