Impacts of seasonality and parasitism on honey bee population dynamics

Authors: CHEN, J. - Arizona State University; RODRIGUEZ RINCON, J. - Arizona State University; DeGrandi-Hoffman, Gloria; FEWELL - Arizona State University; HARRISON, J. - Arizona State University; KANG, Y. - Arizona State Geological Survey

Submitted to: Journal of Mathematical Biology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/11/2023
Publication Date: 6/30/2023
Citation: Chen, J., Rodriguez Rincon, J., Hoffman, G.D., Fewell, Harrison, J., Kang, Y. 2023. Impacts of seasonality and parasitism on honey bee population dynamics. Journal of Mathematical Biology. 87. Article 19. https://doi.org/10.1007/s00285-023-01952-2.
DOI: https://doi.org/10.1007/s00285-023-01952-2

Interpretive Summary: Annual rates of honey bee colony losses have remained at over 30% for more than two decades. There are several reasons for colony loss including stress from poor nutrition, parasites and pathogens, pesticides, and the effects of climate change. Understanding the dynamics of colony loss is difficult because the timing of a stress event can determine if the colony will recover or perish. To better understand impacts of stress from Varroa mites on colony growth and survival, we constructed a theoretical model and included seasonal egg laying and brood rearing rates. We found that depending on season and brood production, Varroa may have either minimal or lethal effects on colony survival. If seasonal effects are prolonged so there is a break in brood production for an extended period, effects from Varroa can cause the colony to collapse. The model can be helpful in identifying critical periods during the year when Varroa must be controlled to avoid colony loss. The model also shows how prolonged seasonal effects such as high temperatures that can occur due to climate change, will increase the impact of Varroa on colony survival, and require an extended period of intervention by beekeepers to avoid colony loss.

Technical Abstract: The honeybee plays an extremely important role in ecosystems and has a tremendous value to our economy. Honey bees and other pollinators are under threat from the combined effects of parasitism, pesticide use, biodiversity loss, and climate change that impact the timing, duration, and variability of seasonality. To understand how parasitism and seasonality influence honey bee colonies separately or interactively, we developed a non-autonomous nonlinear honeybee-parasite interaction differential equation model that incorporates seasonality into the egg-laying rate of the queen. Our theoretical results show that parasitism negatively impacts the honey bee population by either decreasing colony size or destabilizing population dynamics through supercritical or subcritical Hopf-bifurcations depending on conditions. Our bifurcation analysis and simulations suggest that seasonality alone may have positive or negative impacts on the survival of honey bee colonies. More specifically, our study indicates that (1) the timing of the maximum egg-laying rate seems to determine when seasonality has positive or negative impacts; and (2) when the period of seasonality is large it can lead to the colony collapsing. Our study further suggests that the synergistic influences of parasitism and seasonality can lead to complicated dynamics that may positively and negatively impact the honey bee colony's survival. Our work partially uncovers the intrinsic effects of climate change and parasites, and provides insights into how best to maintain or improve a honey bee colony's health.