Fungal endophytes of an endangered tree vary with stress and microenvironment in an ex situ conservation nursery

Premise Plants in ex situ conservation nurseries acquire diverse fungal associates that may be moved among nurseries or into the wild during outplanting, including fungal endophytes that contribute to a broad range of functions and occur in leaves, sometimes alongside pathogens. To improve understanding of fungal symbionts in a plant of high conservation concern, we characterized foliar fungal endophytes of Torreya taxifolia , one of the world's most threatened conifers, in an ex situ conservation nursery. Methods We used culture‐based and culture‐free approaches to characterize fungal endophytes in leaves of T. taxifolia over 2 years and evaluated how endophytes varied spatially and as a function of environmental, plant‐specific, and edaphic factors. We also contrasted them with fungi in other plants (local species and species cultivated at a regional scale) and with soil fungi. Results Culture‐free methods revealed species‐rich and phylogenetically diverse foliar fungal endophytes of T. taxifolia that vary spatially, reflecting symbiont acquisition from nearby plants, environmental factors, and plant stress. Endophyte community composition is subject to both stochasticity and temporal turnover and differs markedly from fungal communities in soils and other plants in the area. Conclusions Our study provides novel insights into factors that can shape fungal endophyte communities for a critically endangered tree species. In addition to identifying local determinants of endophytic symbioses, our work illustrates that plants in conservation nurseries host rich foliar fungal communities of potential importance in plant germplasm protection.