Modularity Promotes Adaptation in a Model of Exploratory Evolution

Biological systems are modular. They are composed of distinct components that function almost independently of one another. Studies have shown that modularity can spontaneously emerge in systems evolving under changing environmental conditions if the goals of evolution are varying in a modular manner or if horizontal gene transfer is present. Here, we examine a model that relaxes these constraints. We analyzed the effect of adding modular organization to a previously characterized model of evolution in gene regulatory networks. In this model, the topology of regulatory interactions is fixed while the regulatory strengths evolve to satisfy a linear constraint on the levels of different regulatory factors. We observed that the probability of successful adaptation within a fixed time period was higher when the regulatory topology was modular. The probability varied non-monotonically with the modularity of the regulatory topology. There are neither modularly-varying goals nor horizontal gene transfer in our model. Our model thus represents a previously uncharacterized scenario wherein modularity can be beneficial in evolving biological systems.