Variation in responses to temperature across admixed genotypes of Populus trichocarpa x P. balsamifera predict geographic shifts in regions where hybrids are favored

Mead, A.; Beasley-Bennett, J. R.; Bleich, A. C.; Fischer, D. G.; Flint, S.; Golightly, J.; Klopf, S. K.; Kulbaba, M. W.; Lasky, J.; LeBoldus, J. M.; Lowry, D. B.; Mitchell, N.; Moran, E. V.; Sexton, J. P.; Sondreli, K. L.; Worthing, B. W.; Zavala-Paez, M.; Fitzpatrick, M. C.; Holliday, J. A.; Keller, S. R.; Hamilton, J. A.

doi:10.1101/2025.05.16.654548

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bioRxiv · 10.1101/2025.05.16.654548

Variation in responses to temperature across admixed genotypes of Populus trichocarpa x P. balsamifera predict geographic shifts in regions where hybrids are favored

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Abstract

O_LIPlastic responses of plants to their environment vary as a result of genetic differentiation within and among species. To accurately predict rangewide responses to climate change, it is necessary to characterize genotype-specific reaction norms across the continuum of historic and future climate conditions comprising a species range. C_LIO_LIThe North American hybrid zone of Populus trichocarpa and P. balsamifera represents a natural system that has been shaped by climate, geography, and introgression. We leverage a dataset containing 45 clonal genotypes from this natural hybrid zone, planted across 17 replicated common garden experiments spanning a broad climatic range. Growth and mortality were measured over two years, enabling us to model reaction norms for each genotype across these tested environments. C_LIO_LISpecies ancestry and intraspecific genomic variation significantly influenced growth across environments, with genotypic variation in reaction norms reflecting a trade-off between cold tolerance and growth. Using modeled reaction norms for each genotype, we predicted that genotypes with more P. trichocarpa ancestry may gain an advantage under warmer climates. C_LIO_LISpatial shifts of the hybrid zone could facilitate the spread of beneficial alleles into novel climates. These results highlight that genotypic variation in responses to temperature will have landscape-level effects. C_LI

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Mead, A., Beasley-Bennett, J. R., Bleich, A. C., Fischer, D. G., Flint, S., Golightly, J., Klopf, S. K., Kulbaba, M. W., Lasky, J., LeBoldus, J. M., Lowry, D. B., Mitchell, N., Moran, E. V., Sexton, J. P., Sondreli, K. L., Worthing, B. W., Zavala-Paez, M., Fitzpatrick, M. C., Holliday, J. A., Keller, S. R., Hamilton, J. A.. 2025-05-22. Variation in responses to temperature across admixed genotypes of Populus trichocarpa x P. balsamifera predict geographic shifts in regions where hybrids are favored. https://doi.org/10.1101/2025.05.16.654548

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