The evolution of plasticity and evolvability in a simple gene regulatory network

Organisms adapt to environmental change by plastic phenotypic responses, genetic adaptation, or a combination of the two. Beyond adapting to the environment, organisms can also evolve the ability to adapt more effectively. Evolution can enhance their capacity to respond to environmental cues (increased plasticity), but also their capacity to harness the effects of mutations (increased evolvability). However, it is unclear how these different adaptive capacities co-evolve. Here, we present an evolutionary simulation study in which a simple gene regulatory network must adapt to various regimes of environmental change. We systematically investigate the evolution of plasticity and evolvability in this network, depending on the speed and predictability of environmental changes, and the reliability of environmental cues. We find that plasticity evolves mostly under fast and erratically changing conditions, especially if cues are reliable. In contrast, evolvability evolves under intermediate environmental variability and lower cue reliability. We zoom in on network architecture to investigate what makes these networks more adaptable, showing that different parts of the network become sensitive to mutations depending on the environmental regime. Overall, our results show that both plasticity and evolvability are readily accommodated even in a simple network, depending on the selective pressures exerted by environmental change.