Diversity and composition of viral communities: coinfection of barley and cereal yellow dwarf viruses in California grasslands

Most species host multiple pathogens, yet field studies
rarely examine the processes determining pathogen diversity within
a single host or the effects of coinfection on pathogen dynamics in
natural systems. Coinfection can affect pathogen transmission and
virulence. In turn, coinfection can be regulated within hosts by interactions
such as cross-protective immunity or at broader spatial
scales via vector distributions. Using a general model, we demonstrate
that coinfection by a group of vectored pathogens is highest with
abundant generalist vectors and weak cross-protection and coinfection-
induced mortality. Using these predictions, we investigate the
distribution of five coexisting aphid-vectored, viral pathogens (barley
and cereal yellow dwarf luteoviruses and poleroviruses) in a native
perennial grass (Elymus glaucus) in both space (700 km) and time
(4 years). Observed coinfection rates were much higher than expected
at random, suggesting that within-host processes ex...