Biological invasions are widespread and contribute to losses of biodiversity at regional and continental scales. A deeper understanding of the mechanisms underlying plant invasions may increase ability to predict invasiveness of plants, predict invasibility of landscapes, and effectively manage invaded lands. The plant-associated microbiome may play a role in invasiveness if microbes more negatively, or less positively impact native plant species than non-native species. Impacts of plant-microbial symbioses on plant performance are mediated by two processes: a plant’s effect on the microbial community and a plant’s response to the microbial community. Although native and invasive plants may or may not have differential effects on the microbial community, differential performance between plant species can be induced if plants have a differential response to the microbial community. Therefore, to gain a performance advantage from the microbial community, an invasive plant must either (1) respond differently than the native plants to a shared microbial community or (2) have a differential effect on and response to the microbial community than the native plants. We explored the degree to which native and non-native lineages of a cosmopolitan plant, Phragmites australis, affected and responded to soil microbial communities in the field and in a controlled experiment.
Results/Conclusions
We found that native and non-native Phragmites differed in effect on and response to microbial communities. However, they did not differ intuitively to explain invasiveness of the non-native lineage. In field populations, native and non-native Phragmites cultivated similar communities of bacteria, fungi, and oomycetes in roots and rhizosphere soils except in the densest, most monotypic stands of each lineage where subtle bacterial community differences emerged. In the greenhouse, bacterial, but not fungal communities differed between experimentally-cultivated soils of each lineage. Native and non-native Phragmites lineages differed in response to similar microbial communities; non-native responded positively to sterile soils whereas native had no response. Similarly, non-native Phragmites responded positively to microbial community disturbance caused by antibiotic application and native Phragmites did not respond. Although native and non-native lineages responded differently to microbial communities, the direction of the response did not explain the invasive properties of the non-native lineage as it responded negatively to the presence of certain microbes and was released from pressure when they were removed, opposite of expectations from the Enemy Release Hypothesis. Separating differential responses from effects increased our understanding of each lineage’s interaction with microbes and may lead to targeted management opportunities.