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).