XVI International Botanical Congess

With the introduction of ultrastructural, biochemical and molecular methods in lichen systematics, traditional genera are abandoned in favour of monophylogenetic entities. However, a negative trend is the recognition of every natural group on genus level. Since taxa with n > 2 elements automatically include subgroups of species more closely related to each other, the logical conclusion of this tendency is a one genus = one species system, with loss of systematic information. It is therefore argued that lichen systematics should apply infrageneric levels, thus far neglected by most workers. Considering that supraspecific taxonomy is an abstract human invention open to individual interpretation, a consensus upon generic concepts is proposed, deducted from rationales provided by evolutionary principles.