Theses and Dissertations

ORCID

0009-0005-5503-0690

Advisor

Basu, Priyadarshini

Committee Member

Harris, Jeffery

Committee Member

Musser, Fred

Committee Member

Krishnan, Natraj

Committee Member

Sagili, Ramesh; Maier, Claudia

Date of Degree

8-12-2026

Original embargo terms

Visible MSU Only 1 year

Document Type

Dissertation - Campus Access Only

Major

Life Sciences (Entomology)

Degree Name

Doctor of Philosophy (Ph.D.)

College

College of Agriculture and Life Sciences

Department

Department of Agricultural Science and Plant Protection

Abstract

Honey bee and pollinator health face serious challenges, with inadequate nutrition and climate change emerging as key factors behind declining pollinator numbers. The first aim of this dissertation was to investigate the pollen nutritional composition of various bee forage plants. Pollen from 85 target forage plant species was analyzed for macro- and micro-nutrients, revealing substantial variation in the pollen nutritional composition. Protein concentrations ranged from 44.4 to 337.4 µg mg-1, lipid from 9.3 to 262.3 µg mg-1, 24-methylenecholesterol from 28.9 to 0.01 mg ml-1, Δ5-avenasterol from 3.58 to 0.02 mg ml-1, β-sitosterol from 41.42 to 0.01 mg ml-1, and concentrations of individual essential amino acids ranged from 465.9 to 0.00 ppm. The second aim of this dissertation was to evaluate the effects of heat and drought stress on the nutritional quality and quantity of plant pollen and nectar, as well as plant physiology. Heat and drought stress did not uniformly impact floral resources or plant physiology; instead, their impact varied with stress duration and the specific floral resource or physiological aspect examined. Specifically, heat increased the overall concentrations of pollen lipids, and drought increased concentrations of certain pollen phytosterols, including key sterols such as 24-methylenecholesterol and β-sitosterol. Additionally, heat rapidly affected metabolite profiles, but drought had a stronger impact over time. Heat stress decreased the amount of nectar fructose, glucose, and sucrose, while most nectar amino acid concentrations increased under heat stress. Prolonged heat and drought stress reduced the availability of floral resources for bees. The third aim of this dissertation was to determine the impacts of heat stress one honey bee physiology and gut microbiome. It was found that while chronic heat stress did not affect honey bee survival, acute heat shock reduced survival by 4% for pollen supplemented bees and by 20% for non-pollen supplemented bees. Additionally, pollen supplementation increased survival under chronic heat stress by 9% and under heat shock by 11%. This study also showed that honey bee microbiome and proteome are adaptive to the effects of heat stress, with temperature stress exerting selective, taxon-specific effects on the gut microbiome rather than causing broad community disruption.

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