Nutritional Ecology of Wild Bees: How Pollen Macronutrient Composition Shapes Development and Survival

Abstract

Bees rely on diverse floral resources to meet their nutritional needs, yet habitat loss, urbanization, and agricultural intensification are altering pollen availability and composition. Understanding the macronutrient profiles of pollen is central for pollinator health, as protein, lipids, and essential fatty acids influence bee development and survival. This thesis explores the nutritional composition of pollen from various plant species and its implications for bee health. Chapter I investigates the macronutrient content of 57 pollen species native to North America, revealing significant variation in non-esterified fatty acids (NEFAs), amino acids (AAs), and protein-to-lipid (P:L) ratios. Asteraceae pollen was particularly rich in essential amino acids, while mixed diets provided a balance of nutrients necessary for bee health. Chapter II examines how pollen macronutrient composition influences larval development in the small carpenter bee (Ceratina calcarata). Experimental rearing on black poplar (Populus nigra) and dandelion (Taraxacum officinale) pollen demonstrated that protein-rich arboreal pollen significantly enhanced bee growth, survival, and developmental rates. Bees on dandelion pollen alone exhibited delayed growth and reduced body size, while mixed diets mitigated nutritional stress. This research highlights the importance of nutritional diversity in pollen sources, emphasizing the role of tree pollen as an overlooked resource for pollinator conservation. As habitat loss and climate change continue to threaten pollinators, ensuring access to high-quality, nutritionally diverse floral resources may be key to sustaining bee populations and promoting ecosystem resilience.