Editing Evolvability (section)

=== Without recombination ===

[[Mutational robustness|Robustness in the face of mutation]] does not increase evolvability in the first sense. In organisms with a high level of robustness, mutations have smaller phenotypic effects than in organisms with a low level of robustness. Thus, robustness reduces the amount of heritable genetic variation on which selection can act. However, robustness may allow exploration of large regions of [[fitness landscape |genotype space]], increasing evolvability according to the second sense.<ref name="Wagner 2005" /><ref name="Masel 2010" /> Even without genetic diversity, some genotypes have higher evolvability than others, and selection for robustness can increase the "neighborhood richness" of phenotypes that can be accessed from the same starting genotype by mutation. For example, one reason many proteins are less robust to mutation is that they have marginal [[Protein folding|thermodynamic stability]], and most mutations reduce this stability further. Proteins that are more thermostable can tolerate a wider range of mutations and are more evolvable.<ref>{{cite journal | vauthors = Bloom JD, Labthavikul ST, Otey CR, Arnold FH | title = Protein stability promotes evolvability | journal = Proceedings of the National Academy of Sciences of the United States of America | volume = 103 | issue = 15 | pages = 5869–74 | date = April 2006 | pmid = 16581913 | pmc = 1458665 | doi = 10.1073/pnas.0510098103 | bibcode = 2006PNAS..103.5869B | doi-access = free }}</ref> For polygenic traits, neighborhood richness contributes more to evolvability than does genetic diversity or "spread" across genotype space.<ref>{{cite journal | vauthors = Rajon E, Masel J | title = Compensatory evolution and the origins of innovations | journal = Genetics | volume = 193 | issue = 4 | pages = 1209–20 | date = April 2013 | pmid = 23335336 | pmc = 3606098 | doi = 10.1534/genetics.112.148627 | author2-link = Joanna Masel }}</ref>