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Evidence of climate-driven selection on both tree traits and trait plasticity across the climatic range of a riparian foundation species
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  • Hillary Cooper,
  • Rebecca Best,
  • Lela Andrews,
  • Jaclyn Corbin,
  • Iris Garthwaite,
  • Kevin Grady,
  • Catherine Gehring,
  • Kevin Hultine,
  • Thomas Whitham,
  • Gerard Allan
Hillary Cooper
Northern Arizona University

Corresponding Author:hillary.cooper@nau.edu

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Rebecca Best
Northern Arizona University
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Lela Andrews
Northern Arizona University
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Jaclyn Corbin
Northern Arizona University
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Iris Garthwaite
Northern Arizona University
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Kevin Grady
Northern Arizona University
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Catherine Gehring
Northern Arizona University
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Kevin Hultine
Desert Botanical Garden
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Thomas Whitham
Northern Arizona University
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Gerard Allan
Northern Arizona University
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Abstract

Selection on quantitative traits by divergent climatic conditions can lead to substantial trait variation across a species range. In the context of rapidly changing environments, however, it is equally important to understand selection on trait plasticity. To evaluate the role of selection in driving divergences in traits and their associated plasticity within a widespread species, we compared molecular and quantitative trait variation in Populus fremontii (Fremont cottonwood) populations throughout Arizona. Using SNP data and genotypes from 16 populations reciprocally planted in three common gardens, we first performed QST-FST analyses to detect selection on traits and trait plasticity. We then explored the mechanistic basis of selection using trait-climate and plasticity-climate regressions. Three major findings emerged: 1) There was significant genetic variation in traits expressed in each of the common gardens and in the phenotypic plasticity of traits across gardens. 2) Based on QST-FST comparisons, there was evidence of selection in all traits measured; however, this result varied from no effect in one garden to highly significant in another, indicating that detection of past selection is environmentally dependent. We also found strong evidence of divergent selection on plasticity across environments for two traits. 3) Traits and/or their plasticity were often correlated with population source climate (R2 up to 0.77 and 0.66, respectively). This suggests that steep climate gradients across the Southwest have played a major role in shaping the evolution of divergent phenotypic responses in populations and genotypes now experiencing climate change.
22 Mar 2022Submitted to Molecular Ecology
29 Apr 2022Reviewer(s) Assigned
13 Jun 2022Review(s) Completed, Editorial Evaluation Pending
28 Jun 2022Editorial Decision: Revise Minor
28 Jul 2022Review(s) Completed, Editorial Evaluation Pending
28 Jul 20221st Revision Received
01 Aug 2022Editorial Decision: Accept
Oct 2022Published in Molecular Ecology volume 31 issue 19 on pages 5024-5040. 10.1111/mec.16645