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.