Heritable Viruses as Hidden Drivers of Insect Phenotypes and Evolution

Recent studies using metatranscriptome sequencing have revealed a diversity of viruses associated with insects. Researchers have used various approaches to establish patterns of transmission of insect-specific viruses and have shown that insects often harbor viruses that are inherited from parents to offspring. It remains unclear, however, whether heritable viral symbioses can be understood in the same ecological and evolutionary framework that has been established for bacterial symbiosis. We review studies showing beneficial and pathogenic effects of heritable viruses on their hosts, and we discuss additional ways that heritable viruses shape insect evolution. We also compare bacterial and viral symbiosis and review ways that this emerging field can be used for biocontrol of pests and insect-borne pathogens. Heritable viruses are a key part of the ecology and evolution of insects. A framework for studying symbiosis between insects and these microbes is important for a comprehensive understanding of insect biology.