Variation in predicted reaction norms in response to mean coldest month temperature (MCMT) across admixed Populus genotypes. The reaction norm of each genotype is shown as a separate line colored by species ancestry, with green indicating Populus trichocarpa and blue indicating Populus balsamifera. Predictions for the overall model (a, d) incorporate both yearly growth increment in centimeters (cm) and the probability of mortality; predictions for the conditional model (b, e) only predict growth, ignoring the probability of zeros arising from other processes including mortality; and predictions for the zero-inflated model (c, f) predict the probability of zeros arising from mortality. (a–c) Responses across the range of MCMT values at garden and home climates. Actual values of home climates (|) and garden climates (circle) used for model training are shown on the x-axis. (d, e) Responses based on distance from climate of origin (garden–home MCMT); positive values indicate a warmer climate and negative values indicate a colder climate. If genotypes perform best in environments similar to their home environment, growth should be highest and mortality should be lowest when the transfer distance is 0.
Maps showing the predicted shift in species ancestry in the Populus hybrid zone, based on genotype-specific responses to mean coldest month temperature (MCMT). In (a, b), the color of the base layer shows the species ancestry of the studied genotype which is predicted to have the highest fitness (as measured by growth and mortality) in that location under historic (a) and future climates (b). (c) The change in optimal species ancestry between future (b) and historic (a) climates, indicating regions where increased Populus trichocarpa ancestry is expected to be beneficial in green, and regions with no change in gray. As MCMT increases, we predict that genotypes with higher P. trichocarpa ancestry may be able to outcompete genotypes with higher Populus balsamifera ancestry in some portions of the P. balsamifera range, favoring a northeastern shift of the P. trichocarpa range and the hybrid zone and into historically colder, more continental regions. Regions with MCMT values outside of the range measured in the common gardens (−13.05°C to 10.85°C) are masked and colored white. Actual ancestry of collected genotypes is shown as circles. Species ranges are shown as dark blue and green outlines (Little, 1971). The same predictions are mapped across North America, including the common garden sites (Supporting Information Fig. S15).
Very happy to see our article comparing the responses of hybrid poplars in 17 common gardens, out now in @newphyt.bsky.social! We estimated reaction norms to predict how warming winters could change where different ancestries are favored.
nph.onlinelibrary.wiley.com/doi/10.1111/...
