ABSTRACT
PREMISE OF THE STUDY: As global climate change alters drought regimes, rapid evolution of traits that facilitate adaptation to drought can rescue populations in decline. The evolution of phenological advancement can allow plant populations to escape drought, but evolutionary responses in phenology can vary across a species' range due to differences in drought intensity and standing genetic variation. METHODS: Mimulus cardinalis, a perennial herb spanning a broad climatic gradient, recently experienced a period of record drought. Here, we used a resurrection study comparing flowering time and stem height at first flower of pre-drought ancestors and post-drought descendants from northern-edge, central, and southern-edge populations in a common environment to examine the evolution of drought escape across the latitudinal range. KEY RESULTS: Contrary to the hypothesis of the evolution of advanced phenology in response to recent drought, flowering time did not advance between ancestors and descendants in any population, though storage condition and maternal effects could have impacted these results. Stem height was positively correlated with flowering time, such that plants that flowered earlier were shorter at first flower. This correlation could constrain the evolution of earlier flowering time if selection favors flowering early at a large size. CONCLUSIONS: These findings suggest that rapid evolution of phenology will not rescue these populations from recent climate change. Future work is needed to examine the potential for the evolution of alternative drought strategies and phenotypic plasticity to buffer M. cardinalis populations from changing climate.
