Simulated winter climate change reveals greater cold than warm temperature tolerance in Chrysolina polita (Coleoptera: Chrysomelidae)

Climate change is expected to lead to rising winter temperatures in temperate zones, coinciding with a decrease in winter snow cover. Insects adapted to winter conditions in the temperate zone might be exposed to changing winter conditions and higher temperature fluctuations, which can affect diapause and mortality. We studied the effects of climate change on Chrysolina polita, a temperate zone species overwintering as an adult in the shallow surface of the soil. We tested the effects of increased and fluctuating temperature on the mortality and body composition of the beetles in a laboratory environment, as well as the effects of snow cover removal on the mortality and body mass in field conditions. We found that in the laboratory study, a 2 °C increase in mean temperature increased mortality and resulted in increased lipid consumption, whereas temperature fluctuation caused desiccation of the beetles but did not affect mortality compared to the control condition. In the field study, the snow removal caused the mean soil temperature to decrease by 3 °C and fluctuate (ranging from -26.4 to 2.5 °C compared to a range of -1.7 to 0.5 °C in the control), yet these differences did not affect beetle mortality or body mass. We conclude that C. polita exhibits greater resistance to cold temperatures than to higher temperatures during diapause. Therefore, the rising temperatures associated with climate change can pose challenges for overwintering.