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

NUÑEZ MARTIN A.; HORTON THOMAS R.; HAYWARD JEREMY; DIMARCO ROMINA D.; SORENSEN MIRIAM; SIMBERLOFF DANIEL

Conferencia; 8th International Conference of Mycorrhiza (ICOM 8); 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 have conducted research on Pinaceae invasions, a major problem in the Southern hemisphere, with a focus on the role of ectomycorrhizal fungi. We used a series of greenhouse, field, and lab studies. We have found that mycorrhizal fungi can be a major factor limiting Pinaceae invasion, with seedling establishment and growth far from plantations being limited by a lack of mycorrhizal inoculum. Also, results from inoculation studies with animal feces showed that animals seem to be the main dispersal vectors of compatible mycorrhizal fungi in the area since field experiments showed that wind dispersal 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 to be promoting invasion fronts of Pinaceae. When seedlings grew connected to a network of exotic trees, they grew significantly bigger than when isolated from such networks. However, in native forest areas distant from any exotic trees, isolation from the native networks was an advantage. This suggests a new mechanism for biotic resistance, where the fungal network of the native trees can reduce the establishment of exotic trees, perhaps through competitive interactions between the native and exotic networks. These results from Isla Victoria suggest that mycorrhizal fungi can 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.