Mounting evidence suggests that rapid evolutionary adaptation may rescue
some organisms from the impacts of ongoing climate change. However,
evolutionary constraints might hinder this process, especially when
different aspects of environmental change generate antagonistic
selection on genetically correlated traits. Here, we use
individual-based simulations to explore how genetic correlations
underlying the thermal physiology of ectotherms might influence their
responses to the two major concomitant components of climate
change---increases in mean temperature and thermal variability. We found
that genetic correlations can influence population dynamics under
climate change, with declines in population size varying three-fold
depending on the type of correlation present. Surprisingly, populations
whose thermal performance curves were constrained by genetic
correlations often declined less rapidly than unconstrained populations.
Our results suggest that accurate forecasts of the impact of climate
change on ectotherms will require an understanding of the genetic
architecture of the traits under selection.