Fig. 3

More variable expression of immunity genes in anthropogenic compared to wild habitats. a Bagplots showing, for wild (above) and all mesocosm (below) fishes, the distribution of individual scores along the 2 major axes of an overall principal components analysis (PCA) of immunity genes; plots show outer hull (a minimally enclosing convex polygon) containing all points, individual points and lines joining individual points to the group centroid. There was a significant difference in variance between wild and mesocosm fishes scores along PC1 (P = 0.024; P = 0.016 if including only mesocosm fishes from un-heated tanks). PC1 accounted for 42 % of total variation and PC2 23 %. Inset in upper panel shows a biplot of variable loadings on PC1 and PC2; vectors emanate from the origin and the axis scales (x : PC1, y: PC2) are indicated in the bottom left corner of the inset. PC1 represented positive covariation in the majority of genes (mostly substantial loadings of the same sign), whilst PC2 represented contrasts between genes (substantial loadings of variable sign), some of which might be explained by opposing seasonal patterns in the wild [23] and the diminution of these patterns in the mesocosms. b Box-and-whisker plot of individual expression values for genes with significant differences in expression variance between wild and mesocosm fishes (Additional file 3: Table S2). Box shows interquartile range (IQR) and median (line); whiskers extend to most distant observations within a 1.5 × IQR distance of the IQR; points show outlying values (>1.5 × IQR distant from IQR)