The evolution of RNA viruses: A population genetics view

RNA viruses are excellent experimental models for studying evolution under the theoretical framework of population genetics. For a proper justificatio n of this thesis we have introduced some properties of RNA viruses that are relevant for studying evolution. On the other hand, population genetics is a reductionistic theory of evolution. It does not consider or make simplis tic assumptions on the transformation laws within and between genotypic and phenotypic spaces. However, such laws are minimized in the case of RNA vir uses because the phenotypic space maps onto the genotypic space in a much m ore linear way than on higher DNA-based organisms. Under experimental condi tions, we have tested the role of deleterious and beneficial mutations in t he degree of adaptation of vesicular stomatitis virus (VsV). a nonsegmented virus of negative strand. We also have studied how effective population si ze, initial genetic variability in populations, and environmental heterogen eity shapes the impact of mutations in the evolution of vesicular stomatiti s virus. Finally, in an integrative attempt, we discuss pros and cons of th e quasispecies theory compared with classic population genetics models for haploid organisms to explain the evolution of RNA viruses.