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

Eukaryotic gene regulatory networks (GRNs) are significantly more complex than those of prokaryotes, yet the selective pressures driving this divergence remain debated. The authors investigated whether reproductive strategy—specifically the presence or absence of genomic recombination—acts as a primary driver of this complexity. Using a biochemically informed in silico model, the researchers simulated the evolution of GRNs over one million generations. They compared populations that reproduced sexually (with recombination) against those that reproduced clonally (without recombination) across various mutation rates, initial network topologies, and environmental conditions.

The study demonstrates that both recombining and non-recombining populations eventually converge to the same level of regulatory complexity, regardless of whether selection is present. This suggests that complexity is not an adaptive trait directly selected for, but rather a byproduct of the evolutionary process. While the final complexity plateau is similar, recombination significantly alters the trajectory toward that state: it slows the emergence of complexity in static environments but accelerates it in changing environments. Furthermore, while recombining populations consistently evolved higher mutational robustness, the researchers found no direct correlation between a network's complexity and its robustness, indicating these two traits evolve independently.

These findings challenge the assumption that the increased complexity of eukaryotic GRNs is necessarily the result of direct adaptive selection. Instead, the results point toward a model where reproductive strategy and environmental stability interact to shape the tempo of evolutionary change. By showing that complexity can emerge neutrally, the paper provides a new perspective on how genomic architecture evolves, suggesting that the differences between prokaryotic and eukaryotic networks may be more closely tied to the fundamental constraints of their respective reproductive and regulatory hardware than previously assumed.

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