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The roles of divergent and parallel molecular evolution contributing to thermal adaptive strategies in trees
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  • Collin Ahrens W,
  • Alexander Watson-Lazowski,
  • Guomin Huang,
  • David Tissue,
  • Paul Rymer
Collin Ahrens W
Western Sydney University Hawkesbury Institute for the Environment

Corresponding Author:collinwahrens@gmail.com

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Alexander Watson-Lazowski
Western Sydney University Hawkesbury Institute for the Environment
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Guomin Huang
Western Sydney University Hawkesbury Institute for the Environment
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David Tissue
Western Sydney University Hawkesbury Institute for the Environment
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Paul Rymer
Western Sydney University Hawkesbury Institute for the Environment
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Abstract

Local adaptation is a major driver of biological diversity, and related species may develop analogous (parallel evolution) or alternative (divergent evolution) solutions to similar ecological challenges. We expect these adaptive solutions between closely related organisms would culminate in both phenotypic and genotypic signals. In this study, we employ a reciprocal transplant, glasshouse experiment with two Eucalyptus species ( E. grandis and E. tereticornis) with large, overlapping distributions grown under contrasting ‘local’ temperature conditions (tropic and temperate) to investigate the independent contribution of adaptation, plasticity, and their interaction at molecular, physiological and morphological levels. We find key traits differ in their response. The link between gene expression and traits markedly differed between species. Divergent evolution was the dominant pattern driving adaptation as unique gene responses (91% of all significant genes) was the greatest factor driving differentiation; but overlapping gene (homologous) responses were dependent on the determining factor (plastic, adaptive, or genotype by environment interaction). 98% of the plastic homologs were similarly regulated, while 50% of the adaptive homologs and 100% of the interaction homologs were antagonistically regulated. Therefore, parallel evolution for the adaptive effect in homologous genes was greater than expected but not in favour of divergent evolution. Further, heat shock proteins for E. grandis were almost entirely driven by adaptive responses, while plasticity drove the response in E. tereticornis. These results suggest divergent molecular evolutionary solutions dominated the adaptive mechanisms among species, even in similar ecological circumstances. Thus, trees with overlapping distributions are unlikely to equally persist in the future, suggesting that management of future forests to changing temperature conditions must be species specific.
19 Aug 2022Submitted to Plant, Cell & Environment
22 Aug 2022Submission Checks Completed
22 Aug 2022Assigned to Editor
23 Aug 2022Reviewer(s) Assigned
16 Sep 2022Review(s) Completed, Editorial Evaluation Pending
18 Sep 2022Editorial Decision: Accept