Testing the evolutionary potential of an alpine plant: Phenotypic plasticity in response to growth temperature outweighs parental environmental effects and other genetic causes of variation

Phenotypic plasticity and rapid evolution are fundamental processes by which organisms can maintain their function and fitness in the face of environmental changes. Here we quantified the plasticity and evolutionary potential of an alpine herb Wahlenbergia ceracea. Utilising its mixed-mating system, we generated outcrossed and self-pollinated families that were grown in either cool or warm environments, and that had parents that had also been grown in either cool or warm environments. We then analysed the contribution of environmental and genetic factors to variation in a range of phenotypic traits including phenology, leaf mass per area, photosynthetic function, thermal tolerance, and reproductive fitness. The strongest effect was that of current growth temperature, indicating strong phenotypic plasticity. All traits except thermal tolerance were plastic, whereby warm-grown plants flowered earlier, grew larger, produced more reproductive stems compared to cool-grown plants. Flowering onset and biomass were heritable and under selection, with early flowering and larger plants having higher relative fitness. There was little evidence for transgenerational plasticity, maternal effects, or genotype-by-environment interactions. Inbreeding delayed flowering and reduced reproductive fitness and biomass. Overall, we found that W. ceracea has the capacity to respond rapidly to climate warming via plasticity, and the potential for evolutionary change.

Methods
Dataset was collected from a large glasshouse experiment of Wahlenbergia ceracea (waxy bluebell) plants grown under two growth temperatures. This experiment follows on from years of controlled environment and controlled crosses to generate F3 lines, including growing the F2 parents under two growth temperatures as well. Phenotypic trait measurements were taken using a variety of standard ecophysiological measurements, and these include measuring flowering onset phenology, chlorophyll content (SPAD units), Leaf Mass per Area (LMA), photosystem II efficiency and capacity (FV/FM, φPSII), heat and cold tolerance (Tcrit-hot and Tcrit-cold from temperature dependent chlorophyll fluorscence; T-F0), biomass, numbers of reproductive stems, seed and capsule mass. Details are provided in full in the manuscript. Post-data collection processing of dataset .csv files were done using R v4.3.1. The R script used for data analyses, Tables, Figures, and supporting data is provided as part of the data archiving as an html Rmarkdown output.