Invasive plant species can disrupt the diversity and composition of native plant communities. However, it is less clear how native and invasive plants influence each other’s microbial communities. Non-native species frequently lose associated microbes, including pathogens, when they establish new ranges. The assembly of microbial communities associated with non-native plants is likely a consequence of whether they were introduced with microbes, how they interact with local microbes, and the composition of the surrounding native plant community. Pathogens that accumulate on introduced species have the potential to regulate invasions and spillover onto native species. To infer the extent to which native and invasive plants influence each other’s pathogenic microbial communities, we characterized, compared, and contrasted the foliar fungal communities of native and invasive grass species in California, where invaders have been present since the mid 19th century, across a gradient of background communities varying in native and non-native plant composition.
Results/Conclusions
We found that native and invasive grass species shared numerous fungal pathogens, including species that are closely related to pathogens of agricultural grains (e.g. species of Pyrenophora, Parastagonospora, and Ramularia). However, specific fungi were isolated at different frequencies between the two plant groups, contributing to divergent pathogen communities. For example, Pyrenophora chaetomioides was a common pathogen on invasive grasses, but was uncommon on native grasses. In addition, some fungi were unique to one of the two plant groups. Fungal pathogen community composition on the focal native and invasive species did not vary with the background composition of native versus non-native grasses. These results suggest that native and invasive grasses acquire foliar fungal pathogens from one another, but that each group shapes their own communities through host-pathogen or microbe-pathogen interactions. These plant-scale interactions prevent pathogenic foliar fungal communities from shifting with changes in the surrounding plant community and could potentially limit the extent to which spillover influences native-invasive interactions.