Research on plant viruses in natural ecosystems has been increasing rapidly over the past decade. This paper reviews recent research on the barley and cereal yellow dwarf viruses (B/CYDVs) in grasslands of the western US, beginning with the evidence that the disease caused by these viruses facilitated the invasion of western US grasslands by European annual grasses. Observational and experimental studies of B/CYDVs were carried out along a latitudinal gradient (33.8-48.8°N) from southern California to southern Canada. The prevalence and community composition of B/CYDVs were assessed over a variety of scales and under a range of biotic and abiotic conditions. The findings indicate that both biotic and abiotic factors are important influences on virus ecology and epidemiology. Introduced annual grasses are high-quality hosts that amplify both virus and vector populations in this system, but our research suggests that endemic perennial grasses are critically important for sustaining virus populations in contemporary grasslands largely composed of introduced species. Experiments indicated that increased phosphorus supply to hosts resulted in greater host biomass and higher virus prevalence. Using experimental exclosures, it was found that the presence of grazing vertebrate herbivores increased the abundance of annual grasses, resulting in increased virus prevalence. The results of these studies suggest that patterns of B/CYDV prevalence and coinfection in western US grasslands are strongly shaped by the interactions of host plants, vectors, vertebrate herbivores, and abiotic drivers including nutrients.
Bibliographical noteFunding Information:
The research described here would not have been possible without the assistance of many people and organizations. Field and lab assistance was provided by M. Dekkers, C. Kahlke, B. Martin, E. Orling, and J. Peters. We also acknowledge the support of the University of California Reserve System (McLaughlin Natural Reserve) , University of California Research and Extension Centers (Hopland REC and Sierra Foothill REC) , and the U.S. Fish and Wildlife Service (Baskett Slough and William L. Finley National Wildlife Refuges) . Support for this research was provided, in part, by NSF grants EF-0525666 and DEB-1015805 to E. T. Borer and E. W. Seabloom, EF-05-25641 and DEB-10-15909 to C.E. Mitchell, and EF-0525669 and DEB-1015903 to A.G. Power as part of the joint NSF-NIH Ecology of Infectious Disease program.
- Barley yellow dwarf virus
- Cereal yellow dwarf virus
- Perennial bunchgrasses