Subpopulation-specific metabolomes under predation risk
The metabolomic responses to fish kairomones differed strongly among
subpopulations. Only a small part of the responsive peaks was shared by
all three subpopulations: 15.9 % (176 of 1105, Figure 3a) for the
positive ion mode, and 23.5 % (136 of 580, Figure 3b) for the negative
ion mode. The total number of differentially regulated peaks to fish
kairomones differed among the subpopulations (positive ion
mode:\(\ x_{2}^{2}\) = 278.39, P < 0.001; negative ion
mode: \(x_{2}^{2}\) = 79.40, P < 0.001, Table S3). The
high-fish subpopulation had the highest number of responsive peaks
(Figure 3, Table S3), indicating that the metabolome of the high-fish
subpopulation changed most strongly in response to fish kairomones.
Projecting the phenotypic trajectories onto the metabolomic PCA
landscape showed that for both ion modes the magnitude of the
multivariate metabolomic reaction norm was greater for the high-fish
subpopulation than the pre-fish (P < 0.001 for both ion
modes) and the reduced-fish (P = 0.026 for the positive, P< 0.001 for the negative ion mode) subpopulations, while the
latter two did not differ in magnitude (Figure 4a-d, Table S4). The
direction of the multivariate plasticity differed considerably between
the pre-fish subpopulation and the two other subpopulations (bothP < 0.001). In contrast, the high-fish and reduced-fish
subpopulations did not differ in the direction of multivariate
plasticity for the positive ion mode (P = 0.086), and only
differed slightly for the negative ion mode (P = 0.047).