Discussion:
We found evidence for divergent selection (QST> FST) acting on leaf phenology and morphology traits measured in three common gardens for 16 different Arizona populations. This result is consistent with a majority of studies finding QST values are generally larger than FST for ecological traits (McKay & Latta 2002; Savoleinen et al. 2007; Leinonen et al. 2013). In addition, we found no or contrasting evidence for selection on performance traits, which also showed a reversal in the relative growth rates of populations grown in hot vs. cold common environments. Below, we discuss the evidence for climate-driven adaptive divergence in leaf traits, local adaptation to climate that this trait divergence may enable, and the potential consequences of both under current climate change.