Evolutionary rescue can be impeded by temporary environmental amelioration - Dataset

Rapid evolutionary adaptation has the potential to rescue from extinction populations experienc- ing environmental changes. Little is known, however, about the impact of short-term environmen- tal fluctuations during long-term environmental deterioration, an intrinsic property of realistic environmental changes. Temporary environmental amelioration arising from such fluctuations could either facilitate evolutionary rescue by allowing population recovery (a positive demo- graphic effect) or impede it by relaxing selection for beneficial mutations required for future sur- vival (a negative population genetic effect). We address this uncertainty in an experiment with populations of a bacteriophage virus that evolved under deteriorating conditions (gradually increasing temperature). Periodic environmental amelioration (short periods of reduced tempera- ture) caused demographic recovery during the early phase of the experiment, but ultimately reduced the frequency of evolutionary rescue. These experimental results suggest that environmen- tal fluctuations could reduce the potential of evolutionary rescue.