Native and non-native trees can find compatible mycorrhizal partners in each other's dominated areas.
Aims: Biological invasions have historically been addressed mostly from an aboveground perspective, so little is known about the impacts of belowground invasions. We studied the impact of belowground invasions on growth of native tree species and test the possibility of novel interactions between native and non-native hosts and native and non-native belowground symbionts. Methods: We combined field and growth chamber studies. With a growth chamber bioassay we compared growth and root colonization percentage of native Nothofagus and non-native invasive pine species, both highly dependent on ectomycorrhizal fungi (EMF), growing in pine invaded and non-invaded soils from native Nothofagus forest. We evaluated the identity of EMF species associated with both hosts in the different soil sources from the bioassay and we performed an in situ root sampling in the field. Results: We found that both hosts grew equally well in both soil sources in terms of biomass, with high percent of root colonization, and no cross-host colonization of symbiotic EMF except for one species of Sistotrema found on both hosts. Conclusions: Soil where invasive hosts are absent is already conditioned by the presence of non-native invasive EMF. Native trees may be able to remain in the invaded area due to the presence of native EMF. The presence of native hosts is not hindering the invasion of non-native hosts and the presence of native belowground fungal mutualists seems not to hinder the spread of their non-native counterparts.