Compensating for climate change-induced cue-environment mismatches: evidence for contemporary evolution of a photoperiodic reaction norm in Colias butterflies.

Anthropogenic climate change alters seasonal conditions without altering photoperiod and can thus create a cue-environment mismatch for organisms that use photoperiod as a cue for seasonal plasticity. We investigated whether evolution of the photoperiodic reaction norm has compensated for this mismatch in Colias eurytheme. This butterfly's wing melanization has a thermoregulatory function and changes seasonally. In 1971, Hoffmann quantified how larval photoperiod determines adult wing melanization. We recreated his experiment 47 years later using a contemporary population. Comparing our results to his, we found decreased melanization at short photoperiods but no change in melanization at long photoperiods, which is consistent with the greater increase in spring than summer temperatures recorded for this region. Our study shows that evolution can help correct cue-environment mismatches but not in the same way under all conditions. Studies of contemporary evolution may miss important changes if they focus on only a limited range of conditions.