| Central to the evolution of RNA viruses is their remarkable capacity to rapidly generate genetic variation and respond to environmental challenges. It is clear that these features drive their evolution during transmission and throughout infections. However, the extent to which they explain RNA virus evolution over deep evolutionary timescales is unknown. Within the first two chapters of this thesis, I examine arthropod paleoviruses related to non-retroviral RNA viruses, addressing questions regarding their formation, co-option and the extent to which they inform our knowledge of RNA virus biodiversity in nature. These projects contribute to advancing our knowledge of past virus-host interactions on many fronts, but one emerging theme is that paleoviral sequences indicate that a much greater level of arthropod RNA virus diversity exists in nature than has been previously appreciated. In following, I target arthropods using total-RNA sequencing methods to search for RNA viruses, and identify members of a divergent lineage belonging the family Bunyaviridae, which I refer to as "phasmaviruses." I characterize the past and present diversity within this group using molecular data from extant members and arthropod paleoviruses, and conclude that it is ancient and has been associated with a broad range of insect hosts. For the host genus Chaoborus, I collect virus and host population datasets from subarctic ponds across North America, taking advantage of the insular nature of host populations to compare phasmavirus evolution among endemic and invading host populations. The results suggest that host demography plays an important role in shaping the evolution of some RNA viruses, and that the unexplored diversity of arthropod RNA viruses in nature may contribute greatly to furthering our understanding of RNA virus evolution.. |
