Resurrected in the field: benefits of rapid adaptation to historic drought seen mainly at the leading edge of a plant species’ range

Montane plant populations are experiencing novel conditions due to climate change. Furthermore, climate change is causing increased climate perturbations, such as the 2012-2016 drought in the western US, remarkable in its aridity, longevity, and warmer temperatures. This drought provided an opportunity to understand how montane populations respond to extreme perturbations, including at species range limits. We resurrected seeds of the endemic annual plant, Erythranthe laciniata, collected before the drought and at the height of the drought, in a common garden experiment to understand how drought influenced evolution in contemporary field conditions. The study included nine populations across the species range, including elevational-based range edges. Over 2,100 replicates were sown in three common gardens at natural populations at low, central, and high elevations. We recorded phenology and flower production to estimate lifetime fitness. This experiment took place in 2021, a year with relatively low precipitation and high temperatures. We found higher fitness in the drought generation at the high garden, as well as the evolution of faster phenology. Additionally, we detected climate adaptation at the low and high gardens. Low-elevation populations outperformed central populations at the central garden, suggesting adaptive lags and mismatch with contemporary climate change. Together, these results indicate rapid contemporary adaptation that is beneficial at the leading edge of the species range. Nevertheless, low fitness at lower elevations may foreshadow range contraction under continued climate change.