FIGURE 2 | Robust phenotypes can lead to a rapid yet neutral exploration of sequence space.

Each rectangle represents part of a space of genotypes. Grey circles correspond to individual genotypes on a neutral network. A straight line links two genotypes if they can be interconverted through a single point mutation. The top three panels show how neutral evolution explores genotype space for a phenotype with low robustness. This is a phenotype with a small neutral network, in which individual genotypes have, on average, few neutral neighbours. The bottom three panels show the same evolutionary process, but for a robust phenotype. All panels contain the same number of genotypes to facilitate comparison. They therefore do not reflect neutral network sizes, but merely the fact that genotypes on large neutral networks also tend to have more neutral neighbours. Blue circles correspond to individual members of a population, and red stubs illustrate hypothetical deleterious mutations that cause a mutation to genotypes lying outside the neutral network (not shown). The differences in the number of red stubs between the top and bottom panels illustrates that robust phenotypes with large neutral networks are subject to fewer deleterious mutations. The two leftmost panels show two genetically identical populations with moderate genotypic diversity, in which several individuals have the same genotype. As these populations evolve through mutation and selection confining them to a network, the population with the robust phenotype will spread more rapidly, because fewer deleterious mutations impede accumulation of genotypic diversity. This phenomenon is independent of population size or mutation rate¹⁰⁹.

Download file

If the slide opens in your browser, select "File > Save As" to save it.

• Download Power Point slide (306 KB)