Analyzing Bee Body Size as a Potential Factor of the Island Rule

Variance in body size of bees can affect multiple factors including pollination ability, floral handling, and response to evolving environmental conditions. Likewise, body size itself is influenced by a range of climate and location-specific environmental factors. Islands represent distinct habitats with unique ecological and climate conditions. Many animals differ drastically in body size in island habitats, but the extent to which this effect occurs in insects is unknown. This phenomenon is known as the “island rule” in which animals are considerably larger on islands when compared to their mainland counterparts. Recognizing these patterns enhances our understanding of how differing environmental conditions between islands and mainlands can drive long-term evolutionary changes in species. I measured body size for each specimen, accounting for sex and missing body parts. In this study, we drew data from the sweat bee, agapostemon subtilior, and measured their body size by mass. My findings suggested that insects, specifically agapostemon subtilior, have evolved to greater sizes on the mainland than on the island. These surprising findings both raise new questions and help clarify the role between habitat factors and body size variation in this important native pollinator.This poster was presented at the UCSB EEMB Undergraduate Research Symposium 2025.