Scattered far and wide: A broadly distributed temperate dune grass finds familiar fungal root associates in its invasive range

- Rich fungal communities occupy the roots of Ammophila arenaria in its invasive range.
- Dominant fungi occupying the roots of Ammophila arenaria are widely dispersed.
- Plant species impacts the community composition of root associated fungi in dunes.
- The community composition of root fungi in the same dune grass differs among dunes.
- Temperature, nitrogen and pH change correlate with fungal community differences in dunes.

Deterministic and stochastic factors interact to generate biogeographic patterns in fungal communities, challenging efforts to predict which fungal assemblages will develop in association with introduced plants. The coastal dune grass Ammophila arenaria has been moved around the world. We sampled A. arenaria roots in its native range in the United Kingdom, and in Australia and New Zealand where it is invasive. The co-occurring native dune grass Leymus arenarius was also sampled in the United Kingdom, and the native dune grass Spinifex sericeus was sampled in Australia and New Zealand. A. arenaria associates with root fungal communities in its invasive range that are richer than those in the United Kingdom, and richer than those in co-occurring native grasses, demonstrating that exotic plants are not necessarily depauperate in fungal associates. Most of the dominant OTUs associating with A. arenaria were shared among all three geographic regions. However, community composition varied among regions, with differences in temperature, nitrogen and pH correlating with community change. Within regions, community composition varied among dunes, although the majority of sequences obtained were in OTUs that were detected in multiple dunes. Host plant species identity influenced fungal community composition, although the majority of the data were in OTUs that were shared between hosts. While the roots sampled appeared healthy, many of the dominant fungi recovered are potentially pathogenic. This study demonstrates that many fungi are widely dispersed, and that introduced plants are likely to associate with functionally diverse fungal communities that include species from their native ranges. However root-associated fungal community composition is variable, even at regional and local scales in a common plant in a common environment.