Elevation-associated variation in bumble bee venom composition is not retained under common-garden conditions

Bumble bees (Bombus) are vital pollinators across diverse habitats. Female bumble bees have a defensive, venomous sting used against predators. Little is known about the factors associated with intraspecific variation in bumble bee venom. We studied the venom composition of wild-caught Bombus vosnesenskii and tested for elevation-associated differences along an elevation gradient in Oregon, USA. Using a common garden approach with laboratory-reared colonies sourced from wild populations, we also tested the influence of captivity on venom response. Proteomic analysis using liquid chromatography-tandem mass spectrometry revealed clear elevation-associated variation in venom composition among wild populations, particularly in the abundance of the bombolitin-like antimicrobial peptide. By contrast, comparable elevation-associated differences were not evident under common-garden conditions when colonies were reared under shared laboratory conditions. More broadly, our findings demonstrate substantial intraspecific variation in bumble bee venom composition, and captive populations may not fully reflect wild variability, impacting the interpretation of venom studies relying on captive species.