Assessing the Interactive Effects of Temperature and Humidity on Bumble Bees
Restricted (Penn State Only)
- Author:
- Cruz, Jules
- Graduate Program:
- Ecology
- Degree:
- Master of Science
- Document Type:
- Master Thesis
- Date of Defense:
- October 31, 2024
- Committee Members:
- Rudolf Johannes Schilder, Thesis Advisor/Co-Advisor
Monica Kersch-Becker, Committee Member
Jason Kaye, Program Head/Chair
Margarita Maria Lopez-Uribe, Thesis Advisor/Co-Advisor
David Andrew Miller, Committee Member - Keywords:
- heat wave
humidity
thermal stress
temperature and humidity
bumble bee
insect
ecophysiology
temperature and humidity interaction
high humidity
evaporative cooling
bumble bee microcolony - Abstract:
- Insects are facing alarming population declines across the globe that have been associated with climate change. The increase of temperature and temperature-related events, such as heat waves, are highly studied factors to explain how biodiversity loss is accelerating. While assessing species responses to the extreme temperatures, it is crucial to consider the variation in humidity that will also be driven by climate change, since ambient humidity can influence evaporative heat loss and thermal performance. Despite the known correlation between temperature and humidity, the effects of this interaction on insect fitness have been poorly investigated. In this thesis, I contribute to the study of insect ecophysiology by (1) presenting a comprehensive review of temperature and humidity effects to insects fitness, highlighting the interaction and discussing potential applications, and (2) experimentally assessing the interactive effects of high humidity and heat waves on pollinator health. Specifically, I exposed the common eastern bumble bee, Bombus impatiens, to a full factorial design integrating a five-day simulated heat wave (33°C) and high humidity (85%). I measured reproductive outputs, feeding behavior, energetic status, and survival and found that heat wave effects were highly dependent on humidity levels. Bumble bees under highly humid heat waves suffered significant reductions in offspring production, pollen consumption, thoracic lipids contents, and queen survival. Heat waves in lower humidity, however, posed neutral or positive effects on bumble bees, including an increase in pollen consumption, growth rates, and number of drones produced in the lab. These results suggest that high humidity can exacerbate potential negative effects of climate change to pollinators, and highlights the need to incorporate humidity as a parameter to temperature studies.