Symbiosis a driver of truffle diversity
(PHYSorg.com Biology)

While the sight of black or white truffle being shaved over on pasta is generally considered a sign of dining extravagance, they play an important role in soil ecosystem services. Truffles are the fruiting bodies of the ectomycorrhizal (ECM) fungal symbionts residing on host plant roots. In many Ascomycota and Basidiomycota lineages, truffle-forming species have evolved independently in nearly every major group. This suggests that symbiosis drives evolution of truffle diversity and selects for specific traits.