Rapid evolution predicts demographic recovery after extreme drought.

Populations that are declining as a result of climate change may need to evolve to persist. Although evolutionary rescue has been demonstrated in theory and in the laboratory, its relevance to natural populations facing climate change remains unknown. Here we link rapid evolution and population dynamics in scarlet monkeyflower, Mimulus cardinalis, during exceptional drought. We leverage whole-genome sequencing across 55 populations to identify climate-associated loci. Simultaneously we track demography and allele frequency change throughout the drought. We establish range-wide population decline during the drought, geographically variable rapid evolution, and variable population recovery that is predictable by standing genetic variation in, and rapid evolution at, climate-associated loci. These findings demonstrate the possibility of evolutionary rescue in the wild, showing that genetic variation at adaptive, but not neutral, loci predicts population recovery. Editor's summary: Extreme weather events are occurring more frequently due to climate change, stressing many species. Plants are particularly vulnerable given their sensitivity to changes in moisture and temperature. Anstett et al. examined 19 populations of scarlet monkeyflower (Mimulus cardinalis) along the west coast of the United States and Mexico over 8 years, including during the most extreme drought on record in this region (see the Perspective by Urban and Balstad). Although several of their monitored populations went extinct locally, the authors found that variants associated with climate shifted frequency in some populations, and populations with more substantial shifts toward alleles favored in hot, dry conditions recovered more quickly. These results suggest that although evolutionary rescue in response to climate stressors is possible, it is not guaranteed. —Corinne Simonti [ABSTRACT FROM AUTHOR]