Intraspecific host variation plays a key role in virus community assembly.

Infection by multiple pathogens of the same host is ubiquitous in both natural and managed habitats. While intraspecific variation in disease resistance is known to affect pathogen occurrence, how differences among host genotypes affect the assembly of pathogen communities remains untested. In our experiment using cloned replicates of naive Plantago lanceolata plants as sentinels during a seasonal virus epidemic, we find non-random co-occurrence patterns of five focal viruses. Using joint species distribution modelling, we attribute the non-random virus occurrence patterns primarily to differences among host genotypes and local population context. Our results show that intraspecific variation among host genotypes may play a large, previously unquantified role in pathogen community structure. The factors that determine whether pathogens co-occur in a host are poorly understood, especially for plant viruses. Here the authors conduct field experiments with the plant Plantago lanceolata and its viruses, showing that viral co-occurrences are driven predominantly by environmental context and host genotype rather than viral interactions. [ABSTRACT FROM AUTHOR]