Abstract
Premise of the studyAs 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 resultsContrary 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.ConclusionsThese 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.
Highlights
Global climate change, including rising temperatures and increases in the frequency and severity of drought (Briffa et al, 2009), is shifting where species occur and how they evolve (Hamann et al, 2018; Parmesan & Yohe, 2003)
Rapid evolution in response to recent climate change has been documented across multiple taxa (Anderson et al, 2012; Franks et al, 2007; Lustenhouwer et al, 2018), suggesting that populations can harbor sufficient genetic variation to respond to climate-induced selection
We performed a resurrection study to assess the evolution of phenology in response to a period of record drought and warming
Summary
Global climate change, including rising temperatures and increases in the frequency and severity of drought (Briffa et al, 2009), is shifting where species occur and how they evolve (Hamann et al, 2018; Parmesan & Yohe, 2003). Populations across a species' range can vary in their abilities to rapidly evolve under climate change due to spatial variation in selection and genetic variation in ecologically important traits. Multiple studies have already found evidence for rapid evolutionary responses to recent climate change in flowering time (Anderson et al, 2012; Franks et al, 2007; Hamann et al, 2018; Thomann et al, 2015). A southern-edge population experienced the most extreme average increase in climatic moisture deficit over the study period (+13.7 mm in S2), whereas another experienced a mean decrease relative to historical conditions (−23.0 mm in S1, Figure 1b), suggesting that the strength of selection on flowering time could vary among populations. We predicted that individuals with earlier flowering times should have shorter stems at the time of flowering due to the shorter growth period prior to first flower
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