Evolutionary simulations reveal role for genomic recombination in the evolution of gene regulatory network complexity and robustness.

The gene regulatory networks (GRNs) of eukaryotes are dramatically more complex than the GRNs of prokaryotes, but we lack a complete picture of the selective pressures that have shaped this difference. Here, we use a biochemically informed model of gene regulation to simulate GRN evolution and explore the role that reproductive strategy plays in shaping regulatory complexity. We find that recombining and non-recombining populations converge to the same level of complexity, even in the absence of selection. However, recombination modifies the rate at which complexity emerges, accelerating convergence to the complexity plateau in changing environments while slowing the process in static environments. Our results suggest that, rather than being under direct selection, regulatory complexity may emerge as a byproduct of other evolutionary processes. These results highlight how reproductive strategy and environmental change interact to influence evolutionary trajectories.