Conclusions
Studies focusing on seedling adaptive potential to multivariate
stressors mimicking changing climatic conditions are timely given the
focus on assisted migration efforts. A multitude of common garden
experiments and genome-wide association studies provide remarkable
evidence for local adaptation and GEI (Langlet, 1971; Savolainenet al ., 2013). Here, we demonstrate strong evidence of adaptive
evolution and GEI at both the per-transcript and co-expression module
levels, with partial evidence that these patterns interact with
interspecific gene flow through the survival component of fitness. We
further highlight that populations of long-lived tree species may be
more able than expected to respond to rapidly changing climatic
conditions through ample genetic variation underlying expression traits
and a modulation of genetic architecture depending on the degree and
direction of environmental change. This response, moreover, appears to
be provided by pleiotropic loci underlying strongly connected adaptive
expression traits. The generality of our primary finding of rapid
adaptive potential aided by pleiotropic loci additionally awaits further
work across phylogenetically diverse tree species distributed across
various climatic gradients with differing demographic histories.