Impact of Invasive Plant Traits and Coexistence on Fungal Community Shifts

Biotic invasions in natural environments reflect not just the impact of the invader but the interplay with the resident community. However, these community-level effects are not well explored. We tested the impact of invasive plant species (Reynoutria japonica and Solidago canadensis) on soil fungal communities and their interactions with native plants. We considered the abundance of invasive species, their distance from native vegetation in trait space, and the time since their introduction using the Biotic Novelty Index (BNIs). The association between BNIs and fungi was group specific. The richness of saprotrophic fungi increased with BNIs, while the richness of arbuscular mycorrhizal fungi decreased in sites invaded by R. japonica. Increasing BNIs was also positively related to soil fungal compositional change, leading to fungal community homogenization and disruption of covariation between native plants and fungi. To estimate the composition of soil communities, we collected 2 teaspoons of soil from each corner and from the centre of the 1 m2 plot, mixed and dried it instantly with silica gel and used it for molecular analyses. Soil DNA was extracted from a 5g subsample of soil collected from each plot using the PowerMax Soil DNA Isolation Kit. To identify the soil fungal community composition, we amplified the target marker region of the ribosomal ITS2 using the degenerate primer pair fITS7:fITS7o and ITS4. The amplified ribosomal ITS2 region were sequenced using a 2x250 bp paired-read sequencing approach on an Illumina NovaSeq platform.