Evolution of phenocopying in a dynamical model of developmental trajectories

Developmental trajectories are known to be canalized, or robust to both environmental and genetic perturbations. However, even when these trajectories are decanalized by an environmental perturbation outside of the range of conditions to which they are robust, they often produce phenotypes similar to known mutants called phenocopies. This correspondence between the effect of environmental and genetic perturbations has received little theoretical attention. Here, we study an abstract regulatory model which is evolved to follow a specific trajectory. We then study the effect of both small and large perturbations to the trajectory both by changing parameters and by perturbing the state in a timed manner. We find, surprisingly, that the phenomenon of phenocopying emerges in evolved trajectories even though the alternative trajectories are not selected for. Our results suggest that evolution simplifies the structure of high-dimensional phenotypic landscapes which can simultaneously show robustness and phenocopying.