Localized reshaping of the fungal community in response to a forest fungal pathogen reveals resilience of Mediterranean mycobiota.

Mediterranean forests are facing the impact of pests such as the soilborne Phytophthora cambivora, the causal agent of Ink disease, and this impact is made more severe by global changes. The status and resilience of the soil microbial ecosystem in areas with such a disturbance are little known; however, the assessment of the microbial community is fundamental to preserve the ecosystem functioning under emerging challenges. We profile soil fungal communities in a chestnut stand affected by ink disease in Italy using metabarcoding, and couple high-throughput sequencing with physico-chemical parameters and dendrometric measurements. Since the site also includes an area where the disease symptoms seem to be suppressed, we performed several analyses to search for determinants that may contribute to such difference. We demonstrate that neither pathogen presence nor trees decline associate with the reduction of the residing community diversity and functions, but rather with microbial network reshaping through substitutions and new interactions, despite a conservation of core taxa. We predict interactions between taxa and parameters such as soil pH and C/N ratio, and suggest that disease incidence may also relate with disappearance of pathogen antagonists, including ericoid- and ectomycorrhizal (ECM) fungi. By combining metabarcoding and field studies, we infer the resilient status of the fungal community towards a biotic stressor, and provide a benchmark for the study of other threatened ecosystems.