Truffle biogeography-A case study revealing ecological niche separation of different species.

Ecology of hypogeic mycorrhizal fungi, such as truffles, remains largely unknown, both in terms of their geographical distribution and their environmental niches. Occurrence of true truffles ( spp.) was therefore screened using specific polymerase chain reaction (PCR) assays and subsequent PCR amplicon sequencing in tree roots collected at 322 field sites across the Czech Republic. These sites spanned a wide range of climatic and soil conditions. The sampling was a priori restricted to areas thought to be suitable for spp. inasmuch as they were characterized by weakly acidic to alkaline soils, warmer climate, and with tree species previously known to host true truffles. Eight operational taxonomic units (OTUs) corresponding to , , , , , , , and were detected. Among these, was the OTU encountered most frequently. It was detected at nearly 19% of the sites. Soil pH was the most important predictor of spp. distribution. preferred weakly acidic soils, and were most abundant in neutral soils, and was restricted to alkaline soils. Distribution of was mainly dictated by climate, with its range restricted to the warmest sites. Host preferences of the individual spp. were weak compared to soil and climatic predictors, with the notable exception that appeared to avoid oak trees. Our results open the way to better understanding truffle ecology and, through this new knowledge, also to better-informed trufficulture.