Fig. 3. Junco thermogenic flexibility correlates with thermal heterogeneity.

a Origin of five Junco populations used in laboratory acclimations (dots) that differ in their native annual temperature range (T_range; values from WorldClim⁶⁶), shown in shaded colors and plotted in R with package raster⁶⁷. Pairwise F_ST indicated by dotted lines and accompanying values in gray. b Thermogenic flexibility, measured as the change in M_sum over the 3-week temperature acclimation treatment (post- minus pre-acclimation), for each population. Boxplots show the median values, the 25th and 75th percentiles (lower and upper margins of the box), and the minimum and maximum values ≤1.5 × IQR from the box margin (whiskers). Dots indicate individual measures (n = 95). Control birds (acclimated to 23 °C) in red; cold-acclimated birds (3 °C) in blue. For each population, the native T_range, number of individuals in each treatment (Control, Cold), and coefficient of variation for cold-acclimated individuals (CV) are shown below. Source data are provided in the Source Data file.