The relative contribution of plasticity and evolution to metabolite changes
For both transitions between two successive periods differing in fish predation pressure we calculated the total peak change of important metabolites (VIP >1), i.e. the peak change as would be observed when comparing the Daphnia under the period-specific kairomone treatments (absence of fish kairomones in the pre-fish and reduced-fish periods, and presence of fish kairomones in the high-fish period), following the method described in (Stoks et al. 2016). We partitioned the total change for each important metabolite into three components: ancestral plasticity, constitutive evolution and evolution of plasticity (see Figure S1 in Supplementary Information). Ancestral plasticity refers to the plasticity present in the older period of a given transition. Constitutive evolution refers to evolution of the mean in the ‘ancestral’ kairomone condition for a given transition between periods, hence in the absence of fish kairomones when going from the no-fish to the high-fish period and in the presence of fish kairomones when going from the high-fish to the reduced-fish period. Evolution of plasticity refers to the change in the slope of the reaction norm and is the remainder of the total trait change after subtracting ancestral plasticity and constitutive evolution from total phenotypic trait change (see Figure S1).