The demographic impacts of shifts in climate means and extremes on alpine butterflies

1. Climate change impacts organismal performance via both shifts in mean conditions and acute thermal stress events. Yet, we know little about the relative fitness impacts of climate means and extremes, and how phenotypes mediate these effects. 2. Here, we incorporate demography in a biophysical model of two alpine butterflies with distinct phenotypes to examine the impacts of recent climate change in the Rocky Mountains of Colorado. 3. The model suggests that shifts in available flight time (mediated by weather means) and egg viability (mediated by weather extremes) over time have varied between phenotypes and along the elevation gradient. Generally, small declines in egg viability may be more than offset by large increases in available flight time at higher elevations. 4. Interactions between environmental conditions and phenotypes may produce unexpected, individualistic responses to climate change.