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 significantly 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 significant part of the diet for large mammals in taiga and tundra ecosystems.

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.

[6] The German naturalist Jonathan Carl Zenker formally introduced the Cladoniaceae to science in 1827, with his work appearing in a publication edited by Karl Goebel.

[13] In recent history, Teuvo Ahti's extensive research, including comprehensive monographs and revisions, has significantly advanced the understanding of Cladoniaceae taxonomy and biogeography.

[25] Some names reference the reddish hue of their fruiting structures, such as "British soldiers" (C. cristatella),[26] the "jester lichen" (C. leporina),[27] and the "lipstick powderhorn" (C. macilenta).

These clades, while generally well-supported by molecular data, often lack clear morphological synapomorphies (shared physical characteristics inherited from a common ancestor), highlighting the challenges in Cladonia taxonomy.

For instance, detailed analyses of the Cladonia furcata complex have revealed high levels of homoplasy (the occurrence of similar traits due to convergent evolution rather than shared ancestry) in the morphological characters traditionally used for species delimitation.

Within the genus Cladonia, mitochondrial genomes span from approximately 45,000 to 66,000 base pairs, consistently containing respiratory genes and ribosomal RNA regions across all examined species.

[36] In 2018, Ekaphan Kraichak and colleagues used a technique called temporal banding to reorganise the Lecanoromycetes, proposing a revised system of classification based on correlating taxonomic rank with geological (evolutionary) age.

[29] The hamathecium (referring to all hyphae between the asci in the hymenium) consists of sparsely branched paraphyses, and is amyloid, indicating that stains blue to blue-black with iodine-based reagents.

Consequently, thin-layer chromatography, a laboratory technique used to separate chemical compounds, is essential for detecting and identifying lichen substances that are present in low concentrations.

[29] Some Pilophorus species form tripartite associations, involving the fungus, green algae, and cyanobacteria within gall-like structures called cephalodia.

This work revealed two distinct ontogenetic types based on the formation of generative tissue and its role in developing the characteristic podetium of Cladonia species.

This demonstrated variability had implications for the taxonomy and phylogenetic relationships within Cladoniaceae, suggesting a complex evolution of reproductive structures that did not strictly align with previously conceived taxonomic groupings.

[57] After more than a century of discovery and research, including recent advances in understanding revealed by molecular phylogenetics studies, the Cladoniaceae encompass 18 genera and more than 500 species.

Following the genus name is the taxonomic authority, year of publication, and the number of species: Myelorrhiza was transferred from the Cladoniaceae to the Ramalinaceae by Sonja Kistenich and colleagues in 2018.

[29] In his 2000 monograph on the Cladoniaceae of the Neotropical realm, Ahti included 184 species in 4 genera, and showed that South America is a hotspot of biodiversity for genus Clanodia.

During the Pleistocene, most species likely survived in areas south of the Cordilleran ice sheet, with some persisting in nunataks, arctic regions, or small coastal refugia.

Cladoniaceae show a preference for specific habitats, with greater floristic and chemical diversity observed in humid areas and lower forested elevations compared to arid regions and alpine zones.

[81] Each of the six Cladoniaceae species that have been assessed by the International Union for Conservation of Nature for the global IUCN Red List face a variety of threats impacting their survival.

[82] Cladonia appalachiensis (endangered, 2020) growing on high-elevation Anakeesta Knob rock, faces threats from visitor disruption and changes in cloud cover and humidity.

[29] The main threats to Cladonia perforata (endangered, 2003) include habitat loss, hurricanes, and improper fire management, with a single natural event potentially causing substantial subpopulation reduction.

Climate change also poses significant risks through altered fire regimes and sea level rise, affecting its pine barren and sand dune habitats.

[29] Pilophorus fibula (endangered, 2020) is threatened by habitat loss, alteration of hydrological regimes, recreational damage, and declining water quality.

[29] Gymnoderma insulare (endangered, 2014), primarily found in old-growth forests in Japan and Taiwan, faces threats from natural hazards like typhoons and is affected by the decline of its tree hosts, Cryptomeria japonica and Chamaecyparis obtusa.

[96] Fruticose Cladonia species, often dyed green and glycerol-treated for flexibility, are common in model train displays as miniature trees and shrubs.

[99] The complex net-like structures of the Australasian lichen Pulchrocladia retipora have been described as "of considerable beauty resembling lace or coral", and have been utilised in floral and architectural design.

According to the lichenologists Robert Lücking and Toby Spribille, "the Cladonia growth form continues to be one of the most widely recognized lichen architectures, with their basal scales and erect, often trumpet-shaped podetia".