Does Robustness Have An Effect On Evolvability
Robust biological systems acquire less phenotypic variation through environmental stressors or genetic damage as compared to less robust systems (Wagner, 2005). The ability of organisms to balance robustness and evolvability is the key for surviving a billion generations of varying environmental conditions with high levels of consistency (Lenski et al, 2006).
An example of robust systems is the ability of some organisms to maintain certain metabolic functions regardless of varying temperature conditions. Another example, in humans, is their ability to proof read DNA and implement DNA repair mechanisms for repair damaged DNA (Lenski et al, 2006).
At a first glance robustness seems to be a major problem faced by evolvability because of an organism’s limited capacity to generate phenotypic variation. Wagner (2005) claimed that this is not the case and two conflicting scenarios can be drawn up for robustness. He claimed that robust systems develop many neutral mutations that cause no phenotypic variation. Natural selection has no effect on these mutations, and thus they can be considered as invincible to evolvability. However the alternative scenario places neutral mutations as the foundation to innovation within a system. Although neutral mutations do no alter primary function within the organism, it is claimed they alter other factors within a system and it is these factors which can lead to evolutionary change as many neutral mutations are acquired over many generations.
So robust systems are actually flexible and can carry out the primary function, with many underlying neutral mutations, but after a certain time frame these mutations will eventually facilitate exaptation (modification in the functionality of a particular trait) (Armbruster, 1997) when there are no more degrees of freedom. Wagner (2005) claimed that this implies robustness has a key role in evolvability.
