The role of ectomycorrhizal fungi in Pinaceae invasions: evidence from Isla Victoria, Argentina.

NUÑEZ, M. A., HORTON, T. R., HAYWARD, J., DIMARCO, R. D., SORENSEN, M. & SIMBERLOFF, D

Arizona

Conferencia; 8th International Conference on Micorriza; 2015

Mycorrhizal fungal invasion and the role of mycorrhizal fungi in plant invasions were historically ignored.There is now enough evidence to show how complex and important belowground interactions in plant invasions are.Here we describe work conducted on Isla Victoria in Nahuel Huapi National Park. During the last 10 years we haveconducted research on Pinaceae invasions, a major problem in the Southern hemisphere, with a focus on the role ofectomycorrhizal fungi. We used a series of greenhouse, field, and lab studies. We have found that mycorrhizal fungi canbe a major factor limiting Pinaceae invasion, with seedling establishment and growth far from plantations being limitedby a lack of mycorrhizal inoculum. Also, results from inoculation studies with animal feces showed that animals seemto be the main dispersal vectors of compatible mycorrhizal fungi in the area since field experiments showed that winddispersal of propagules from sporocarps is limited. With a large field experiment (320 pots under different treatments,10 liters each of intact soil monolith), we have found that mycelial networks associated with exotic Pinaceae seem tobe promoting invasion fronts of Pinaceae. When seedlings grew connected to a network of exotic trees, they grewsignificantly bigger than when isolated from such networks. However, in native forest areas distant from any exotictrees, isolation from the native networks was an advantage. This suggests a new mechanism for biotic resistance, wherethe fungal network of the native trees can reduce the establishment of exotic trees, perhaps through competitiveinteractions between the native and exotic networks. These results from Isla Victoria suggest that mycorrhizal fungican play a complex and important role in tree invasion. It is clear from these results that studying ectomycorrhizal treeinvasion without studying their mycorrhizal symbionts can lead to an incomplete understanding of the invasion process.