Fig. 4. Mapping the location and effect of Midwest introgressions in the Atlantic subpopulation.
a, Positions of all high-frequency (present in >10 genotypes, n = 1,640) introgressions from Midwest into the Atlantic subpopulation are coloured by significance in the two redundancy analyses for climate (blue, n = 234), biomass and survival (green, n = 329) or ‘climate–fitness overlap’, which are significant in both (gold, n = 245). NS, not significant. b, Introgressions are strongly associated with a more upland phenotype among 135 genotypes. For each genotype, the position along the first discriminant axis between ecotypes (Extended Data Fig. 2) is scaled relative to the median Atlantic ecotype value, then plotted and coloured by the proportion of introgressed sequence in each significance bin from a. c, The introgression ranks from b were converted to a purple–orange colour scale (right of b) and georeferenced positions of collection sites for each library are plotted for the northern Atlantic seaboard of the USA. Publicly available cultural and physical GIS layers were accessed with the rnaturalearthdata R package51.