Shifts in ectomycorrhizal fungal community composition during the early establishment of native and exotic pine seedlings

Exotic pine trees are often introduced to novel places worldwide. How exotic pines interact with local microbial communities, such as symbiotic ectomycorrhizal (ECM) fungi, during early establishment compared to interactions by their native counterparts remains to be examined in detail. In this study, native masson pine (Pinus massoniana) and exotic slash pine (Pinus elliottii) seedlings were grown in field-collected soil cores. ECM root tips were collected 3- and 6-months after planting and fungi were identified using high-throughput sequencing. We found that host identity was a key factor determining ECM fungal community assembly after 3-months: native pines associated with Rhizopogon while exotic pines associated primarily with ECM generalists. After 6-months growth, however, ECM fungal communities in native and exotic pines were both dominated by Rhizopogon species. We also found that host selections of several pioneer ECM fungi shared by both native and exotic pines may facilitate an exotic pine's establishment. These findings indicate that more attention should be paid to ECM fungal community shuffling by exotic trees during early establishment and, in turn, the influence of the potential changes in ECM fungal communities on local forest ecosystems.