The evolution of modularity in genome architecture

It has been suggested that the capacity to evolve can itself evolve. One factor that may be important in determining evolvability is modularity of the genotype-phenotype map. A related phenomenon is modularity in genome architecture, in which genes with epistatic effects are colocalized on the chromosome. This changes a population’s response to recombination by maximizing recombination among genes with additive effects and minimizing recombination of genes with epistatic interactions. The effects and origins of genome modularity were investigated using a computational model, in which a population of individuals evolved in a changing fitness landscape under mutation and recombination. Populations with modular genomes evolved faster than did populations with non-modular genomes. Moreover, in long runs that started with nonmodular genomes but allowed inversion, populations evolved high levels of genome modularity. This demonstrates that over long time periods, evolvability can itself evolve through reorganization of the genome. The results may explain some observations of genome modularity in bacteria and other organisms.