Figure 4.

Median net F₂ hybrid misregulation under varying mutation rates occurring at cis-regulatory sites of separate traits in the pleiotropic (open boxes) and two-domain (shaded boxes) models. Mutation rates are expressed as multiples (0.125–8) of the baseline mutation rate of 8.333 × 10⁻⁵/bit. (A) Median net F₂ misregulation of the positively selected trait as a function of varying the overall mutation rate. Misregulation was constrained to lower levels in the pleiotropic model relative to the two-domain model and the extent of constraint increased with mutation rate. (B) As in A, but instead varying the mutation rate only at the cis-regulatory locus of the conserved trait. Misregulation was again constrained in the pleiotropic model relative to the two-locus model, but was not sensitive to mutation rate. (C) Misregulation of the conserved trait as a function of the mutation rate at the cis-regulatory locus of the positively selected trait. In the pleiotropy model, misregulation was high at low mutation rates, dropping to zero as mutation rate increases, but no misregulation occurred in the two-domain model. Box plots show median, quartiles, and full ranges. Simulation conditions: directional selection was applied over the course of 4000 generations; population size = 400.