Selection analyses
Selection on several traits differed between high and low greenhouse watering levels (Fig. 2). In line with the field experiment, selection for early flowering was stronger under low watering in both traits (days to flowering × watering: χ2=13.6, df=1, p<0.001, blow=-0.3, bhigh=-0.08; leaf number at flowering × watering: χ2=9.4, df=1, p=0.003, blow=-0.25, bhigh=-0.1). Similarly, high reproductive allocation was stronger selected for under low than under high watering (reproductive allocation × watering: χ2=114.6, df=1, p<0.001, blow=0.7, bhigh=0.35). Among these three traits showing rapid evolution in the field, genetic correlations were relatively strong and in the direction of their joint selection (Appendix Fig. S3).
Among traits without significant rapid evolution, low watering selected stronger against high vegetative biomass (vegetative biomass × watering: χ2=17.1, df=1, p<0.001, blow=-0.24, bhigh=0.1, Fig. 2). In contrast, greater plant height was overall favored (b=0.15, χ2=11.1, df=1, p=0.001) without difference between watering levels (height × watering: χ2=0.21, df=1, p=0.65, Fig. 2). Since vegetative biomass and plant height showed a positive genetic correlation (Appendix Fig. S3), this suggests conflicting selection on these traits under low watering. No differential selection was found for stomata density (χ2=2.16, df=1, p=0.17, Fig. 2).