  Conventional population genetics considers the evolution of a limited number
of genotypes corresponding to phenotypes with different fitness. As model
phenotypes, in particular RNA secondary structure, have become computationally
tractable, however, it has become apparent that the context dependent effect of
mutations and the many-to-one nature inherent in these genotype-phenotype maps
can have fundamental evolutionary consequences. It has previously been
demonstrated that populations of genotypes evolving on the neutral networks
corresponding to all genotypes with the same secondary structure only through
neutral mutations can evolve mutational robustness [Nimwegen {\it et al.}
Neutral evolution of mutational robustness, 1999 PNAS], by concentrating the
population on regions of high neutrality. Introducing recombination we
demonstrate, through numerically calculating the stationary distribution of an
infinite population on ensembles of random neutral networks that mutational
robustness is significantly enhanced and further that the magnitude of this
enhancement is sensitive to details of the neutral network topology. Through
the simulation of finite populations of genotypes evolving on random neutral
networks and a scaled down microRNA neutral network, we show that even in
finite populations recombination will still act to focus the population on
regions of locally high neutrality.
