Squamarinaceae

The Cladoniaceae are a family of lichen-forming fungi in the order Lecanorales, comprising about 560 species distributed amongst 18 genera. This family is one of the largest among lichen-forming fungi and is globally distributed, from Arctic tundra to tropical rainforests, favouring humid environments while being intolerant of arid conditions. Molecular phylogenetics has substantially advanced the understanding of their complex taxonomic history, revealing intricate evolutionary relationships and leading to a refined classification. Notable members include reindeer moss and cup lichens of the genus Cladonia, which consist of about 500 species and forms a major part of the diet for large mammals in taiga and tundra ecosystems.

A distinctive feature of many Cladoniaceae species is their dimorphic thallus: a scaly or crust-like primary form and a fruticose (shrub-like) secondary form known as a podetium or pseudopodetium. These lichens typically grow on soil, decaying wood, or tree trunks, with a few species found on rocks. They form symbiotic associations with green algae, usually from the genus Asterochloris. The family is known for its diverse secondary metabolites—over 70 have been identified—which play roles in species identification and ecological functions such as protection against UV radiation and herbivore deterrence. Genomic studies have uncovered considerable variation in mitochondrial DNA among Cladoniaceae species, and this variation has helped clarify relationships within the family.