Protea repens whole transcriptome count data for control and drought treatment for 8 populations, climatic data for the 8 populations and phenotypic data collected, and data used for linear mixed models for climate gene expression/trait correlation testing

Long term environmental variation often drives local adaptation and leads
to trait differentiation across populations. Additionally, when traits
change in an environment-dependent way through phenotypic plasticity, the
genetic variation underlying plasticity will also be under selection.
These processes could create a landscape of differentiation across
populations in traits and their plasticity. Here, we performed a dry-down
experiment under controlled conditions to measure responses in seedlings
of a shrub species from the Cape Floristic Region, the common sugarbush
(Protea repens). We measured morphological and physiological traits, and
sequenced whole transcriptomes of leaf tissues from 8 populations that
represent both the climatic and the geographic distribution of this
species. We found that there is substantial variation in how populations
respond to drought, but we also observed common patterns such as reduced
leaf size and leaf thickness, and upregulation of stress- and
down-regulation of growth-related gene groups. Both high environmental
heterogeneity and milder source site climates were associated with higher
plasticity in various traits and co-expression gene networks. Associations
between traits, trait plasticity, gene networks and the source site
climate suggests that temperature may play a bigger role in shaping these
patterns when compared to precipitation, in line with recent changes in
the region due to climate change. We also found that traits respond to
climatic variation in an environment dependent manner: some associations
between traits and climate were apparent only under certain growing
conditions. Together, our results uncover common responses of P. repens
populations to drought, and climatic drivers of population differentiation
in functional traits, gene expression and their plasticity.