In lichens, a phylum refers to the major taxonomic rank of the fungal partner (mycobiont). Most lichen-forming fungi belong to the phylum Ascomycota, while a smaller number occur in Basidiomycota. The phylum reflects deep evolutionary relationships rather than the symbiotic lifestyle itself.

In lichens, a class refers to a major taxonomic rank of the fungal partner, grouping related lichen-forming fungi with shared evolutionary history and structural traits. Most lichens belong to the class Lecanoromycetes, while several other ascomycete and basidiomycete classes contribute smaller numbers of lichenized species.

In lichens, an order is a taxonomic rank of the fungal partner that groups related lichen-forming genera sharing common evolutionary origin, reproductive structures, and ecological traits. Major lichen orders, such as Lecanorales and Teloschistales, help organise lichen diversity and support identification, classification, and ecological interpretation.

In lichens, a family is a taxonomic rank of the fungal partner that groups closely related genera sharing similar morphology, reproductive structures, chemistry, and evolutionary history. Families such as Parmeliaceae or Lecanoraceae help organise lichen diversity and provide a practical framework for identification and comparative ecological studies.

In lichens, a genus is a taxonomic rank of the fungal partner that groups closely related species sharing distinctive morphological, anatomical, chemical, and genetic characteristics. Lichen genera (e.g. Lecanora, Parmelia, Cladonia) provide the primary framework for identification, classification, and communication in lichenology.

In lichens, a species is the basic taxonomic unit of the fungal partner, defined by a unique combination of morphology, anatomy, chemistry, genetics, ecology, and reproductive traits. A lichen species represents a distinct evolutionary lineage, even though it exists as a symbiosis with specific photosynthetic partners.