{{Short description|Genus of lichen-forming fungi}} {{Use dmy dates|date=June 2025}} {{Use Oxford spelling|date=June 2025}} {{Automatic taxobox | image = | image_caption = | taxon = Epilichen | authority = Clem. (1909) | type_species = ''Epilichen scabrosus'' | type_species_authority = (Ach.) Clem. (1909) | subdivision_ranks = Species | subdivision = ''E. glauconigellus''<br /> ''E. scabrosus''<br /> ''E. stellatus'' }}

'''''Epilichen''''' is a small genus of lichen-forming fungi in the family Rhizocarpaceae.<ref name="CoL_CD73T"/> These parasitic lichens live on other lichens, beginning as thin, crust-like patches that may break into small islands or scales, and in some cases produce no visible body at all except for their reproductive structures. They reproduce through black, disc-shaped fruiting bodies that contain distinctive brown spores with a "doughnut ring" appearance, and can eventually take over the space occupied by their host lichen once it dies.

==Taxonomy==

The genus was proposed by the American ecologist Frederic Clements in 1909, with ''E.&nbsp;scabrosus'' assigned as the type species. Clements originally classified the genus in the family Patellariaceae.<ref name="Clements 1909"/>

==Description==

''Epilichen'' species parasitise other lichens and begin as thin, crust-like patches (crustose thalli) that may fracture into island-like {{lichengloss|areoles}} or develop minute scales (subsquamulose lobes). In some cases the lichen produces no visible thallus at all, emerging only as reproductive bodies on its host. A distinct {{lichengloss|prothallus}} (border of fungal hyphae) and a protective outer skin ({{lichengloss|cortex}}) are both absent, and the genus lacks the powdery or bud-like outgrowths (soralia and isidia) that many lichens use for asexual spread. The photosynthetic partner is always a green alga with rounded cells (a {{lichengloss|chlorococcoid}} photobiont).<ref name="Fryday et al. 2024"/>

Sexual reproduction occurs in black, disc-shaped apothecia that lack a {{lichengloss|thalline margin}}, so the only border is the {{lichengloss|true exciple}}, a dark, compact ring of fungal tissue. A thin brown {{lichengloss|epithecium}} coats the top of the hymenium, while a thick, dark-brown {{lichengloss|hypothecium}} lies beneath. Threads called {{lichengloss|paraphysoids}} weave through the hymenium, branching and re-joining to form a loose net but seldom swelling at the tips. The asci are long, club-shaped sacs; when treated with potassium iodide solution they turn blue (K/I+), a diagnostic amyloid reaction caused by the {{lichengloss|tholus}} (the thickened apex) and the surrounding gelatine. Each ascus releases brown ascospores divided by a single wall; a torus-shaped thickening encircles the septum, giving the spores a distinctive "doughnut ring" appearance. No asexual pycnidia have been observed in the genus. Chemically, the genus contains two pulvinic acid pigments that lend yellow tones, along with several unidentified secondary metabolites. Although ''Epilichen'' is obligately lichenicolous, it may form its own independent thallus once the host lichen's fungal partner dies, effectively inheriting the space it first exploited.<ref name="Fryday et al. 2024"/>

==Species==

* ''Epilichen glauconigellus'' {{au|(Nyl.) Hafellner (1979)}}<ref name="Hafellner 1978"/> * ''Epilichen scabrosus'' {{au|(Ach.) Clem. (1909)}} * ''Epilichen stellatus'' {{au|Triebel (1989)}}<ref name="Triebel 1989"/>

==References== {{Reflist|refs=

<ref name="Clements 1909">{{cite book |last=Clements |first=F.E. |year=1909 |title=The Genera of Fungi |location=Minneapolis |publisher=H.W. Wilson |pages=69, 174 |url=https://www.biodiversitylibrary.org/page/2892763}}</ref>

<ref name="CoL_CD73T">{{Catalogue of Life |id=CD73T |title=''Epilichen'' |access-date=25 July 2024}}</ref>

<ref name="Fryday et al. 2024">{{cite book |last1=Fryday |first1=A. |last2=Möller |first2=E.J. |last3=Timdal |first3=E. |last4=Yahr |first4=R. |last5=Cannon |first5=P. |last6=Coppins |first6=B. |last7=Sanderson |first7=N. |last8=Simkin |first8=J. |year=2024 |title=Rhizocarpales, including ''Catolechia'', ''Epilichen'', ''Haugania'', ''Poeltinula'' and ''Rhizocarpon'' (Rhizocarpaceae), and ''Sporastatia'' and ''Toensbergia'' (Sporastatiaceae) |series=Revisions of British and Irish Lichens |volume=41 |page=3 |url=https://britishlichensociety.org.uk/sites/default/files/Rhizocarpales.pdf}}</ref>

<ref name="Hafellner 1978">{{cite journal |last=Hafellner |first=J. |year=1978 |title=''Catolechia'' Flotow ex Massalongo emend. Körber und Epilichen Clements ex Hafellner--zwei nahe verwandte Flechtengattungen |trans-title=''Catolechia'' Flotow ex Massalongo emend. Körber and ''Epilichen'' Clements ex Hafellner--two closely related lichen genera |journal=Nova Hedwigia |volume=30 |issue=1–4 |pages=673–695 |doi=10.1127/nova.hedwigia/30/1979/673 |language=de}}</ref>

<ref name="Triebel 1989">{{cite journal |last=Triebel |first=D. |year=1989 |title=Lecideicole Ascomyceten. Eine Revision der obligat lichenicolen Ascomyceten auf lecideoiden Flechten |trans-title=Lecideicolous Ascomycetes. A revision of the obligately lichenicolous ascomycetes on lecideoid lichens |journal=Bibliotheca Lichenologica |volume=35 |page=136 |language=de}}</ref>

}}

{{Taxonbar|from=Q5382988}}

Category:Rhizocarpaceae Category:Lecanoromycetes genera Category:Lichen genera Category:Lichenicolous lichens Category:Taxa described in 1909 Category:Taxa named by Frederic Clements