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Greater adaptation potential to climate change in populations of Quercus macrocarpa closer to edges of latitudinal gradient than those from mid-latitudes

Rea, Lucy1; Ostrowsky, Laura2; Mohn, Rebekah3; Garner, Mira4; Worcester, Lindsey3; Lapadat, Cathleen1; McCarthy, Heather5; Hipp, Andrew3

Published Jan 23, 2026 on Dryad. https://doi.org/10.5061/dryad.xwdbrv1ps

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Abstract

With climate change ongoing, tree populations will encounter variable selection pressures that may lead to local extinction if they are unable to adapt or respond appropriately. We use a reciprocal transplant experiment with the widespread tree species, Quercus macrocarpa L., across a latitudinal gradient to predict responses to selection expected with climate change. We asked 1) Is there genetic variation within populations for traits relevant to climate change? 2) Are there differences in direction and strength of selection for these traits in each garden? and 3) Do northern populations have evolutionary potential to adapt to selection in warmer, southern gardens? To address these questions, we estimated genetic variance for three sets of three traits grouped by physiology, spectral wavelengths, and morphology. We then conducted selection analysis to estimate directional and stabilizing selection on each of the traits in each garden and for each population. We used the Breeder’s equation to estimate the response to selection for each trait to assess their evolutionary potential. Our results indicate that traits related to morphology and growth are under strong directional selection in warmer gardens. We also found that populations closer to the edges of the species’ range have a high potential to adapt to climate change, due to their responses to selection in the warmest garden. We found low genetic variance in the population in the middle of the range, which may be a result of lower environmental stress. These results can help inform strategies to improve species resilience in the face of climate change as they tell us which populations are likely to be able to adapt to climate change, so managers planning assisted migration can source seeds from populations likely to adapt to climate change.