Data and code from: Drivers of intraspecific trait variation and drought response of a dominant North American great plains grass: Disentangling the role of climate and genetic background

Intraspecific trait variation (ITV) is critical for plant adaptation,
especially under increasing droughts. ITV results from both phenotypic
plasticity and genetic differentiation, so understanding its sources
improves insight into population adaptation to drought. This study
examines how climate history and genetics shape ITV and drought responses
in Andropogon gerardi, a foundational US Great Plains grass. To quantify
climatic determinants of ITV, we conducted a common garden greenhouse
experiment with 25 A. gerardi populations sourced across broad temperature
(4–21°C, Minnesota-Texas, USA) and precipitation (350–1400 mm yr⁻¹
Colorado-North Carolina) gradients, and we measured 17 functional traits.
To test if drought is the main selective pressure on ITV, we subjected
eight populations across a precipitation gradient (470–1350 mm yr⁻¹) to
experimental drought (15% moisture, 30% control). To assess the genetic
bases of ITV, we genotyped A. gerardi populations. To compare genetic and
environmental effects, we compared greenhouse and field traits from the
same populations. We hypothesized the following: climate-of-origin,
especially precipitation, predicts ITV: dry populations would exhibit
drought-adaptive traits (higher water-use efficiency, shorter stature)
while wet populations would show competitive traits (greater height,
biomass). Experimental drought reduces growth and delays flowering, with
wet populations more affected than pre-adapted dry populations. ITV
corresponds with population-level genetic differentiation, and if ITV has
a strong genetic control, measurements from field and greenhouse settings
should align closely. Precipitation and aridity were the strongest ITV
predictors. PCA revealed wet populations had competitive traits (larger
leaf area, taller), while arid populations had drought-adaptive traits
(higher water-use efficiency, reduced stature). Under drought, wet
populations experienced greater declines in biomass and photosynthesis
than dry populations, highlighting drought as a key selective pressure.
Congruent genetic and trait PCAs confirmed a strong genetic basis for ITV.
Consistent trait patterns across greenhouse and field settings further
support genetic control of ITV. Our findings show that ITV is shaped by
climate-of-origin—particularly precipitation—through coordinated
genetically based trait responses. This work highlights the need to
incorporate ITV and genetic background into conservation and restoration
to improve the selection of resilient populations, helping to sustain
grasslands under future droughts.