Genotype-Phenotype Maps Maximizing Evolvability: Modularity Revisited |
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Authors: | Mihaela Pavlicev Thomas F Hansen |
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Institution: | 1.Department of Biology, Centre for Ecological and Evolutionary Synthesis,University of Oslo,Oslo,Norway;2.Department of Theoretical Biology,University of Vienna,Vienna,Austria |
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Abstract: | The mechanisms translating genetic to phenotypic variation determine the distribution of heritable phenotypic variance available
to selection. Pleiotropy is an aspect of this structure that limits independent variation of characters. Modularization of
pleiotropy has been suggested to promote evolvability by restricting genetic covariance among unrelated characters and reducing
constraints due to correlated response. However, modularity may also reduce total genetic variation of characters. We study
the properties of genotype-phenotype maps that maximize average conditional evolvability, measured as the amount of unconstrained
genetic variation in random directions of phenotypic space. In general, maximal evolvability occurs by maximizing genetic
variance and minimizing genetic covariance. This does not necessarily require modularity, only patterns of pleiotropy that
cancel on average. The detailed structure of the most evolvable genotype-phenotype maps depends on the distribution of molecular
variance. When molecular variance is determined by mutation-selection equilibrium either highly pleiotropic or highly modular
genotype-phenotype maps can be optimal, depending on the mutation rate and the relative strengths of stabilizing selection
on the characters. |
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