Lack of knowledge on ecological determinants and cryptic lifestyles hinder our understanding of Terfezia diversity

Developing below the soil surface desert, truffles are hard to find. Within Terfezia genus, at least 18 species are described and many are endemic to the Mediterranean basin. Ecological and geographic information are key factors for species diagnosis, and so far Terfezia species are believed to be linked to either acidic or basic soils or to specific plant hosts. Thus, we have looked at Terfezia diversity within a relatively homogeneous geographical area in Portugal that is suitable for these species and that covered different soils and different dominant host species. We analyzed the observed intraspecific variability within the context of species ecological preferences (e. g. edaphic and putative host). One of our major findings was the discovery of T. grisea in acid soils in association with Tuberaria guttata, a puzzling information since, until now, this species was only found in alkaline soils. We also report on the linkage of different Terfezia lineages within species and ecologic parameters such as soil texture, soil pH and plant host. Additionally, by placing the collected specimens on the most recent genus phylogeny based on the ITS region, we also updated the number of known Terfezia species occurring in Portugal from three to ten. Terfezia dunensis is here reported for the first time for Portugal. Overall, our results show that the exploration of undersampled sites reveals itself as a good strategy to disclose unknown aspects of desert truffle diversity and ecology. These aspects are of prime importance when considering the economic value of the desert truffles for rural populations in the Mediterranean basin.