Abstract
Airborne fungi and their ecological functions have been largely ignored in plant invasions. In this study, high-throughput sequencing technology was used to characterize the airborne fungi in the canopy air of the invasive weed Ageratina adenophora. Then, representative phytopathogenic strains were isolated from A. adenophora leaf spots and their virulence to A.adenophora as well as common native plants in the invaded range was tested. The fungal alpha diversities were not different between the sampling sites or between the high/low part of the canopy air, but fungal co-occurrences were less common in the high than in the low part of the canopy air. Interestingly, we found that the phytopathogenic Didymellaceae fungi co-occurred more frequently with themselves than with other fungi. Disease experiments indicated that all 5 Didymellaceae strains could infect A. adenophora as well as the 16 tested native plants and that there was large variation in the virulence and host range. Our data suggested that the diverse pathogens in the canopy air might be a disease infection source that weakens the competition of invasive weeds, a novel phenomenon that remains to be explored in other invasive plants.
Highlights
It has been suggested that invasive plants have the ability to decrease biodiversity in local ecosystems through competition [1]
Airborne spores were concentrated from 1000 liters of air (~5mins), using a 9cm diameter Petri dish filled with a sterilized cellulose acetate membrane by a surface air system (SAS) Super ISO 180 (VWR International PBI SRL, San Giusto, Italy)
The alpha diversities, including the Shannon index and species richness, were different neither between the regions nor between the high (HC) and low (LC) parts of the canopy (Fig 1, P > 0.05, paired t test), but there was a large variation within sites
Summary
It has been suggested that invasive plants have the ability to decrease biodiversity in local ecosystems through competition [1]. The enemy release hypothesis (ERH) partially explains this competitive advantage, as hosts in the introduced range escape from their enemies [2,3,4,5,6,7]. Klironomos (2002) showed that five of North America’s most damaging exotic plant invaders modified the soil microbial community in ways that benefit themselves (i.e., positive feedback) [8]. Callaway et al (2004) found a switch from negative to positive plant-soil feedback for spotted knapweed when moving from its native to its exotic range [9].
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