Climatic variation allows montane willows to escape an adaptive trade-off

Area of Science:

• Plant ecology
• Climate change adaptation
• Evolutionary biology

Background:

• Plant population persistence relies on adaptive responses to climate change, driven by heritable variation in stress tolerance.
• Identifying populations that avoid trade-offs among performance traits is crucial for predicting future adaptive capacity.
• The spatial relationship between climate variables can influence the extent of adaptive trade-offs.

Purpose of the Study:

• To investigate climate-driven ecotypic variation in Lemmon's willow (Salix lemmonii).
• To test for trade-offs between drought and freezing sensitivity and growth.
• To determine if spatial decoupling of climate variables allows populations to escape adaptive trade-offs.

Main Methods:

• Common garden study of 90 Salix lemmonii genotypes from 38 sites in the Sierra Nevada.
• Assessed ecotypic variation in leaf turgor loss point (drought sensitivity) along a spring snowpack gradient.
• Measured spring freezing sensitivity in relation to minimum May temperature.

Main Results:

• Significant ecotypic variation in drought sensitivity (leaf turgor loss point) was observed, ranging from -0.95 to -0.74 MPa.
• Variation in spring freezing sensitivity correlated with minimum May temperatures.
• No trade-offs were detected between drought and freezing sensitivity, as the relevant climatic gradients were spatially uncorrelated in the study region.

Conclusions:

• Lemmon's willow populations in the Sierra Nevada exhibit adaptive variation in stress tolerance.
• Spatially decoupled climate variables in this region allow populations to escape adaptive trade-offs.
• Regions with decoupled climate variables may serve as important reservoirs of heritable adaptive phenotypic variation for plants facing climate change.