Virus infection in remnant native bunchgrasses from invaded California grasslands.

This study examined the effects of infection with barley and cereal yellow dwarf viruses (BYDVs) on wild grass species in California, a region in which native perennial bunchgrasses have been largely replaced by exotic annual grasses. We sought to determine whether these widespread viruses compromise the fitness of wild hosts and thus have the potential to influence grassland dynamics. Plant viruses have been long overlooked in ecological studies, and their influence on wild hosts has often been assumed to be minimal. We examined the short-term and long-term consequences of infection on field-grown individuals from 18 different populations of wild California grasses (from seven native and one exotic species). Barley yellow dwarf virus infection was aggressive in most hosts and markedly impaired host fitness by reducing growth, survivorship, and fecundity. Previous work indicates that the presence of exotic grasses can more than double BYDV incidence in natives. Given the ubiquity of BYDVs, our results suggest that apparent competition and other virus-mediated processes may influence interactions among native and exotic grasses and potentially contribute to shifts in grassland community composition.