Phenotypic plasticity and adaptive evolution contribute to advancing flowering phenology in response to climate change

TLDR

Climate change has already shifted the timing of key life‑history events, but the relative roles of phenotypic plasticity and adaptive evolution in driving these phenological shifts remain unclear. The study combines a 38‑year field survey with quantitative genetic experiments to evaluate adaptation to climate change. The authors examined Boechera stricta, a Rocky Mountain mustard, using long‑term phenological data and quantitative genetics to assess adaptive responses. Flowering in Boechera stricta advanced from 1973 to 2011, driven by warmer temperatures and earlier snowmelt, with strong directional selection favoring earlier flowering; quantitative genetics predict a 0.2–0.5‑day per generation acceleration that could explain over 20% of the observed shift, indicating that adaptation will be essential for long‑term persistence under ongoing climate change.

Abstract

Anthropogenic climate change has already altered the timing of major life-history transitions, such as the initiation of reproduction. Both phenotypic plasticity and adaptive evolution can underlie rapid phenological shifts in response to climate change, but their relative contributions are poorly understood. Here, we combine a continuous 38 year field survey with quantitative genetic field experiments to assess adaptation in the context of climate change. We focused on Boechera stricta (Brassicaeae), a mustard native to the US Rocky Mountains. Flowering phenology advanced significantly from 1973 to 2011, and was strongly associated with warmer temperatures and earlier snowmelt dates. Strong directional selection favoured earlier flowering in contemporary environments (2010–2011). Climate change could drive this directional selection, and promote even earlier flowering as temperatures continue to increase. Our quantitative genetic analyses predict a response to selection of 0.2 to 0.5 days acceleration in flowering per generation, which could account for more than 20 per cent of the phenological change observed in the long-term dataset. However, the strength of directional selection and the predicted evolutionary response are likely much greater now than even 30 years ago because of rapidly changing climatic conditions. We predict that adaptation will likely be necessary for long-term in situ persistence in the context of climate change.