Discussion:
We found evidence of selection acting on both traits and trait
plasticity across our three common gardens. In addition, regressions
between traits and provenance climate indicate that much of the
selection detected with QST-FST analysis
is driven by climatic clines to which these populations are locally
adapted. The result of mostly high QST values for traits
is consistent with a majority of studies finding QST is
generally larger than FST for ecological traits (McKay
& Latta 2002; Savoleinen et al. 2007; Leinonen et al.2013). However, our result of divergent selection acting on trait
plasticity is quite striking in light of the relatively few examples of
selection on plasticity documented in the literature (Arnold et
al. 2019). Combining QST-FST analysis
on trait plasticity with plasticity-climate regressions can help uncover
the evolutionary forces shaping plasticity differences across
environmental gradients (Whitlock 2008; Josephs 2018; Kelly 2019).
Below, we discuss the evidence for climate-driven adaptive divergence in
traits and trait plasticity, local adaptation to climate, and the
potential consequences of both under current climate change.