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Systematics, Evolution, and Biodiversity

Student Competition 10-Minute Paper

Student MUVE and SysEB: Behavior, Genetics, and Biodiversity On-Demand Presentations

2nd Place: Fluctuating temperatures as a predictor of eastern spruce budworm defoliation

On-Demand

Presenting Author(s)

Emily Black (she/her/hers)

Master's Student
The University of British Columbia
Vancouver, British Columbia, Canada

Co-Author(s)

Katie Marshall

Assistant Professor
The University of British Columbia
Vancouver, British Columbia, Canada

The eastern spruce budworm (Choristoneura fumiferana) is a Lepidopteran pest of coniferous forests across Canada whose outbreaks lead to significant landscape-scale defoliation damage. The geographic range of the eastern spruce budworm is determined by their tolerance for stressful abiotic factors such as freezing temperatures. Freezing can cause chilling injury and reduce energy stores, and previous studies show that the frequency of fluctuations at sub-zero temperatures is important when predicting eastern spruce budworm overwintering survival rates. However, the relationship between fluctuating temperatures and spruce budworm outbreak distribution and severity has not been explored. I used a species distribution model to evaluate the importance of temperature fluctuations on the distribution and severity of eastern spruce budworm outbreaks. I combined publicly available maps of eastern spruce budworm outbreaks between 2014-2021 in Ontario and Quebec with climate, temperature fluctuation, and forest composition variables to generate a species distribution model. My model correlated these variables with historical outbreak distribution and severity, then evaluated each variable’s importance in predicting spruce budworm outbreaks. I found climate, food abundance, and temperature fluctuations were important factors for models predicting eastern spruce budworm defoliation. I also found temperature fluctuations were more important for determining outbreak severity rather than range. While the response of defoliation to temperature fluctuations differed between provinces, increasing temperature fluctuations were correlated with decreased defoliation severity in Quebec. These results reveal the previously overlooked importance of temperature fluctuations on spruce budworm distribution and can inform models predicting spruce budworm outbreaks for forest management purposes.