Wild Camellia japonica specimens in the Shimane prefecture (Japan) host previously undescribed AMF diversity

The native range of the broadleaf evergreen Camellia japonica L. includes natural non-model ecosystems that have been largely overlooked in the investigation of the diversity of arbuscular mycorrhizal fungi (AMF). Despite a recent overview of the AMF assemblages associated in the naturalized range of C. japonica, no such survey has ever been carried out within the native range of this plant species. For this reason, we examined through 454 sequencing the diversity and structure of AMF assemblages in camellia roots and surrounding soil from four locations within the Shimane prefecture (Japan), a region that harbors native C. japonica trees. The specific objectives were as follows: (i) to evaluate the differences between the root-colonizing and the soil-dwelling AMF community through different measurements of diversity and (ii) to evaluate if and how deeply the small-scale environmental changes affect the structure of AMF assemblages. We found that a large number of AMF (∼90%) could not be assigned to previously known phylotypes, suggesting the occurrence of several undescribed taxa. Diversity was generally higher in roots than in soil samples and the level of dominance was low. Almost 70% of soil-dwelling AMF were retrieved inside the roots and also community structure was very similar between the two niches. Most AMF clades/genera were infrequent and only Rhizophagus/Sclerocystis and Glomus sensu lato were very abundant in both root and soil samples. Above all, soil Fe and Mg content, soil C/N ratio, and the distance from the nearest source of saline water were consistently correlated with AMF community shifts at the local scale.