Contrasting responses of plant, soil fungal and above-ground arthropod communities to plant invasion across latitudes

1. The proliferation of alien species that can suppress resident species via biotic interactions represents a growing concern worldwide. Yet, how above- and below-ground communities simultaneously respond to plant invasion, particularly across large spatial scales, remains poorly explored. We hypothesized plant invasion has a greater impact on recipient above- and below-ground communities at lower than higher latitudes given that biotic interactions play a more significant role in shaping communities in more favorable, lower latitude environments.
2. To test this hypothesis, we conducted a comprehensive field survey of 124 sites spanning a 1700 km latitudinal gradient in China, to explore the effects of invasion of Alternanthera philoxeroides, a globally widespread invasive plant, on plant, soil fungal and above-ground arthropod communities.
3. Invasion of A. philoxeroides had divergent effects on beta diversity (i.e., variation in taxa composition among sites) of plants, above-ground arthropods, and soil saprotrophic fungi, with negative, neutral, and positive responses, respectively. Notably, the compositional dissimilarity of plant and arthropod communities between adjacent invaded and non-invaded sites remained constant across latitudes. In contrast, the compositional dissimilarity of the entire and pathogenic fungal communities between adjacent invaded and non-invaded sites increased with latitude. This resulted in a decreasing difference in invasion effects on the composition of plant and fungal communities with increasing latitude.
4. Synthesis. Our study provides novel insights into the complexities of invasion effects by revealing contrasting responses of above- and below-ground communities to plant invasion across latitudes. The contrasting responses could weaken or reshape above- and below-ground interactions, and, in turn, affect future species invasions and the functioning of terrestrial ecosystems.