Invasion by Two Plant Species Affects Fungal Root Colonizers

The effects of multiple invasive plants on soil fungal communities may impact native ecosystems differently than invasion by one species alone. Native plant communities are likely to have a differential above and below ground response to invaders, and therefore understanding fungal implications of invader interactions would be useful when considering restoration strategies. We examined how invasion by European species, Dog-strangling vine or DSV (Vincetoxicum rossicum) (also pale swallow-wort) and garlic mustard or GM (Alliaria petiolata), can alter root colonization by both the total and arbuscular mycorrhizal fungi. In two different sites in the Greater Toronto Area, we investigated fungal communities associated with each plant species in differing invasion scenarios using terminal restriction length polymorphism analysis. Fungal communities in DSV changed significantly in the presence of GM, with decreased colonization densities observed in both the total fungi (Student's t-test; t = 2.1, p = 0.02) and AMF communities (Student's t-test; t = 2.0, p = 0.03), as well as decreased overall phylotype richness of the total fungal communities associating with DSV growing in GM patches relative to those growing separately from GM in both sites (one-way ANOVA; F = 4.4, p = 0.02). The converse was not observed, suggesting that GM has the dominant effect on the invaded soil environment. These results suggest that multiple plant invaders influence the composition of soil fungi available to natives in a manner that is less predictable than invasion by a single species, possibly via increased carbon provision or antibiosis attributable to unique root exudates.