A Brief Overview of the Systematics, Taxonomy, and Ecology of the Tuber rufum Clade

The Tuber rufum clade is one of the most speciose of clades in the Tuberaceae and is found in the Northern Hemisphere primarily in Asia, Europe, and North America. The species are ectomycorrhizal with angiosperms in neutral to high pH soils. The Rufum clade consists of an estimated 43 species, of which only 18 have been described. Molecular data suggests that five of the described species are species complexes: Tuber candidum, Tuber ferrugineum, Tuber lucidum, Tuber lyonii, and T. rufum. More than half of the undescribed species are from North America. Morphologically, the Rufum clade is characterized by smooth to minutely verrucose peridia and spiny to spiny-reticulate ascospores, although a few species are coarsely verrucose and one species has no spore ornamentation (Tuber melosporum). Tuber lyonii, from Eastern North America, is the only commercially valuable species. It remains to be seen if all species in the T. lyonii complex are commercially valuable.