Ancient alleles drive contemporary climate adaptation in an alpine plant.

Adaptive evolution is key for species to persist in a warming climate. However, how adaptive genetic variants arise and shape both past and future evolutionary trajectories remains largely unknown. In this work, we integrate genomics with functional and ecological assays to unravel the evolutionary history and adaptive potential of alleles governing adaptation to climate through flowering time in an Alpine carnation. We reveal that "warm" and "cold" alleles of the flowering inhibitor CENTRORADIALIS (DsCEN/2) originated through recombination of highly divergent haplotypes during the carnation radiation, implicating ancestral variation in seeding climate-adaptive alleles. These alleles survived in glacial refugia before mediating the species' range expansion in response to postglacial warming. We predict that, by recapitulating past evolution, warm alleles will continue to facilitate adaptation under future climate change. Editor's summary: Many cold-adapted plants will either need to expand their ranges or genetically adapt to the warming temperatures caused by climate change. Fior et al. assembled a draft genome of the alpine wood pink (Dianthus sylvestris) and looked for signatures of selection in high- and low-elevation populations. They identified the gene DsCEN/2, the two main haplotypes of which determine flowering time and segregate at different frequencies between low- and high-elevation populations. The low-elevation haplotype seems to have arisen during range expansion to warmer valleys during the Last Glacial Maximum. Given its fitness benefits to larger plants in warm conditions, this haplotype will likely increase in frequency in high-elevation populations with future temperature increases. —Corinne Simonti [ABSTRACT FROM AUTHOR]