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Vesicular Stomatitis VirusEvolution of virus specialists and generalists
Arthropod-borne viruses (arboviruses) are able to infect arthropods (insects, ticks) as well as other host organisms. For this reason, arboviruses typically encounter alternating host environments in the wild, and have evolved to feature very broad host ranges. We use the RNA arbovirus vesicular stomatitis virus (VSV) (Fig. 3) as a model to examine the evolutionary and molecular genetics of host adaptation. One study allowed VSV to evolve on either of two novel hosts (selection for specialist viruses), or in environments where the two novel hosts fluctuated in time (selection for generalist viruses) (Turner and Elena 2000, Genetics 156:1465-1470). Specialists evolved increased performance on the novel host, at the expense of reduced performance in the alternate host. In contrast, generalists improved their fitness in both novel habitats. These findings contradict the idea that weaker response to selection causes generalists to be disadvantaged relative to specialists. Current work examines the evolution of genetic architecture in our collection of derived specialists and generalists. How do these differing phenotypes map at the molecular level? Are genomic changes in each group highly conserved? Alternatively, do differing adaptive solutions to the same environmental challenges cause populations in each group to genetically diverge? Ongoing research examines the importance of spatially-structured environments in the evolution of VSV, and differing rates of adaptation in specialist and generalist viruses. |
