Abstract
BackgroundThe ability for an evolving population to adapt to a novel environment is achieved through a balance of robustness and evolvability. Robustness is the invariance of phenotype in the face of perturbation and evolvability is the capacity to adapt in response to selection. Genetic robustness has been posited, depending on the underlying mechanism, to either decrease the efficacy of selection, or increase the possibility of future adaptation. However, the true effect of genetic robustness on evolvability in biological systems remains uncertain.ResultsHere we demonstrate that genetic robustness increases evolvability of thermotolerance in laboratory populations of the RNA virus φ6. We observed that populations founded by robust clones evolved greater resistance to heat shock, relative to populations founded by brittle (less-robust) clones. Thus, we provide empirical evidence for the idea that robustness can promote evolvability in this environment, and further suggest that evolvability can arise indirectly via selection for robustness, rather than through direct selective action.ConclusionOur data imply that greater tolerance of mutational change is associated with virus adaptability in a new niche, a finding generally relevant to evolutionary biology, and informative for elucidating how viruses might evolve to emerge in new habitats and/or overcome novel therapies.
Highlights
The ability for an evolving population to adapt to a novel environment is achieved through a balance of robustness and evolvability
Our results showed that variants of RNA virus φ6 that were previously determined to be advantaged in their relative genetic robustness [10], were advantaged in terms of their relative evolvability: greater capacity to undergo adaptive change in a novel environment
Our empirical data are highly valuable for advancing general understanding of evolutionary biology, because we demonstrated that robustness and evolvability can be positively correlated in a biological system
Summary
The ability for an evolving population to adapt to a novel environment is achieved through a balance of robustness and evolvability. Evolvability may be defined as the capacity to adapt in response to selection [1,2,3], or alternatively as the ability to access evolutionary innovations [4,5] These varied definitions echo the diverse opinions on how evolvability might be influenced by aspects of genetic architecture, especially genetic robustness – phenotypic constancy in the face of mutational change [6]. A robust population may be envisioned as residing in a region of a fitness landscape that is relatively flat, owing to the high proportion of resident genotypes in the population that are equal (neutral) in fitness [7]. If environmental change alters the fitness landscape, a robust population may experience an evolvability advantage because newly-arising mutations occur in a (page number not for citation purposes)
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