Graphs illustrating co-evolution and counter-adaptation. A, Correlated evolution of the darts and glands. B, Correlated evolution between stylophores and glands. C, Counter-adaptation of diverticulum in response to changes in the dart. D, Counter-adaptation of the spermatophore's tail (formed by the flagellum) in response to changes in SRO complexity. The principal components used to create the graphs are those obtained from the independent contrasts based on the BI tree without phylogenetic uncertainty. The ellipses represent the 95% confidence interval, Pearson correlations (R) and P-values are indicated in each graph.