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Updated: May 12, 2026

Field-Based Thermal Physiology Assay: Cold Shock Recovery under Ambient Conditions
Published on: March 9, 2021
Variability in winter climate and winter extremes reduces population growth of an alpine butterfly
Jens Roland1, Stephen F Matter
1Department of Biological Sciences, University of Alberta, Edmonton, Alberta T6G 2E9, Canada. jroland@ualberta.ca
Abstract:
We examined the long-term, 15-year pattern of population change in a network of 21 Rocky Mountain populations of Parnassius smintheus butterflies in response to climatic variation. We found that winter values of the broadscale climate variable, the Pacific Decadal Oscillation (PDO) index, were a strong predictor of annual population growth, much more so than were endogenous biotic factors related to population density. The relationship between PDO and population growth was nonlinear. Populations declined in years with extreme winter PDO values, when there were either extremely warm or extremely cold sea surface temperatures in the eastern Pacific relative to that in the western Pacific. Results suggest that more variable winters, and more frequent extremely cold or warm winters, will result in more frequent decline of these populations, a pattern exacerbated by the trend for increasingly variable winters seen over the past century.
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