High voltinism, late-emerging butterflies are sensitive to interannual variation in spring temperature in North Carolina.

Climate change has been repeatedly linked to phenological shifts in many taxa, but the factors that drive variation in phenological sensitivity remain unclear. For example, relatively little is known about phenological responses in areas that have not exhibited a consistent warming trend, making it difficult to project phenological responses in response to future climate scenarios for these regions. We used an extensive community science dataset to examine changes in the adult flight onset dates of 38 butterfly species with interannual variation in spring temperatures in the Piedmont region of North Carolina, a region that did not experience a significant overall warming trend in the second half of the 20th century. We also explored whether voltinism, overwintering stage, and mean adult flight onset dates explain interspecific variation in phenological sensitivity to spring temperature. We found that 12 out of 38 species exhibited a significant advance in adult flight onset dates with higher spring temperatures. In comparison, none of the 38 species exhibited a significant advance with year. There was a significant interaction between mean onset flight date and voltinism, such that late-emerging, multivoltine species tended to be the most sensitive to spring temperature changes. We did not observe a significant correlation between phenological sensitivity and the overwintering stage. These results suggest that butterfly arrival dates may shift as temperatures are projected to rise in the southeastern United States, with late-emerging, multivoltine species potentially exhibiting the greatest shifts in adult flight onset dates.