Co-invasive ectomycorrhizal fungi alter native soil fungal communities

Abstract

Purpose: Pinaceae (pine family) trees are native to the Northern Hemisphere and their invasion into the Southern Hemisphere is a growing problem threatening biological diversity. Pinaceae are ectomycorrhizal (ECM) and their invasions are facilitated by non-native and co-invasive ECM fungi. Nothofagaceae species (southern beeches) are dominant overstory trees across large swaths of the Southern Hemisphere and are the only widespread ECM trees native to southern South America (SSA). This observational study investigates the in situ impact of Pinaceae invasions upon native soil fungi associated with Nothofagaceae hosts in SSA. Methods: We performed soil nutrient testing and metabarcode sequencing of fungi in the rhizosphere of Nothofagus antarctica and Nothofagus dombeyi invaded by Pinaceae trees to determine whether co-invasive fungi might impact native soil fungi. Sampling transects extended from invasions into adjacent Nothofagus stands without invasive Pinaceae. Results: The fungal community composition of the Nothofagaceae rhizosphere was dominated by plant-associated Mortierellaceae OTUs in metabarcode data. Mortierellaceae OTU relative abundance was significantly reduced near invasions of Pinus contorta (Pinaceae). Invasions of Pseudotsuga menziesii (Pinaceae) and Pinus contorta were associated with reduced relative abundance of Nothofagus-associated ECM OTUS in the Nothofagus rhizosphere. Pinus contorta invasions were also associated with reduced soil organic matter, total carbon, total phosphorus, and total nitrogen. Conclusion: Further empirical study is warranted to investigate the hypothesis that Mortierellaceae and Pinaceae-specific /suillus-rhizopogon ECM fungi compete for nutrients bound in soil organic matter. Such competition may have potential long-term legacy effects upon post-invasion restoration efforts and implications for Pinaceae invasions globally.