Context is key: How interactive stressors affect honey bee (Apis mellifera) physiology across caste and life stage

The western honey bee (Apis mellifera) is a key component of our modern agricultural system that faces numerous health challenges from a mixture of biotic and abiotic factors; chief among them are poor nutrition, pesticide exposure, and pathogen infection. These factors can also interact with one another, often in unexpected ways. Studies of individual factors are valuable but often fail to account for interacting stressors and therefore, the proper context. To address this shortcoming, I used a combination of cage assays, in vitro larval rearing, toxicity bioassays, and quantitative PCR to investigate the effects of interactive stressors on honey bee physiology across both caste and life stage. To examine the interactive effects of stressor interactions, I studied how diet (artificial and natural pollen), field-relevant pesticide concentrations (a chlorpyrifos-fungicide mixture, lambda-cyhalothrin, and thiamethoxam), and virus infection (Israeli acute paralysis virus) influence honey bee survival, infection intensity, and gene expression. My findings provided evidence that natural pollen diets nutritionally buffer honey bees against the interactive effects of pesticide and virus, but also that each diet-pesticide combination can produce dramatically different responses, with certain pairings even inducing hormetic responses in bees. These findings suggest that multi-stressor interactions are both complex and context-dependent with great potential to affect bee health and physiology. To investigate the potential detoxification ability of gut microbial symbionts, I exposed honey bee larvae to the butenolide insecticide flupyradifurone or the phytochemical amygdalin and inoculated them with Bombella apis, an ostensible nutritional mutualist. By measuring honey bee survival, mass, and eclosion time, I showed that external supplement did not affect bee response individually. However, when flupyradifurone and B. apis were combined, they synergistically reduced larval survival. These findings show how the purportedly beneficial role of gut symbionts can be shaped by environmental influences, serving as an important reminder for the consideration of context when evaluating the role of gut microbial symbioses. Finally, to improve understanding of queen health and consequently, colony reproductive health, I compared the tolerance of age-matched queen and worker bees to two major insecticides (lambda-cyhalothrin and imidacloprid) belonging to different pesticide classes (pyrethroids and neonicotinoids) and measured expression of their detoxification genes. Queens displayed insecticide tolerance between 5-21 times greater than that of workers and also appear to modulate expression of key detoxification genes. These data help establish groundwork for the contextualization of pesticide exposure effects in queens and eventual development of regulatory tests on honey bee reproductive fitness.

Name thesis:degree_name

Ph.D.

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Entomology

Grantor

University of Illinois at Urbana-Champaign

Year dc:date

2024

Author dc:creator

• Hsieh, Edward M

Contributors dc:contributor

• Dolezal, Adam G
• Berenbaum, May R
• Alleyne, Marianne
• Suarez, Andrew
• Cáceres, Carla

• Honey Bee
• Pesticide
• Nutrition
• Virus
• Microbiome
• Interaction
• Queen
• Toxicology
• Detoxification

Statement dc:rights

• Copyright 2024 Edward Hsieh

Language dc:language

en, eng

Handle dc:identifier

https://hdl.handle.net/2142/127247

OAI record oai:identifier

https://www.ideals.illinois.edu/oai-pmh?verb=GetRecord&metadataPrefix=etdms&identifier=oai%3Awww.ideals.illinois.edu%3A2142%2F127247