What is in a name? Terfezia classification revisited.

Desert truffles (mycorrhizal hypogeous Ascomycota) are found in arid and semi-arid areas of the globe and have great ecological and economic importance. Terfezia is undoubtedly the most diversified of all desert truffle genera, but its taxonomy is far from resolved. Specifically, the large number of newly described species plus the high intraspecific morphological variability observed within some Terfezia lineages as rendered the use of molecular techniques mandatory for specimen's discrimination. But the subsequent increasing amount of sequence data produced also a huge number of undescribed taxa that required determination. We compiled and used the public available ITS data on Terfezia spp. on the custom-curated UNITE database to reconstruct the genus phylogeny. We found at least 17 distinct lineages within the genus and successfully resolved some of the more pressing taxonomic issues, namely the T. leptoderma/olbiensis complex and some misapplied synonymy. Based on this resolved phylogeny, and motivated by the recent new described species, we proposed an identification key to Terfezia genus highlighting the importance of morphological and ecological characterization.