Micarea is a genus of lichen-forming fungi in the family Ectolechiaceae. The widely distributed genus contains 156 species[3] and new species are described actively. Species in the genus are crustose lichens and their photobiont (the non-fungal organism) is a single-celled green alga.[4] The genus was established by the Swedish mycologist Elias Fries in 1825. Micarea lichens are typically small and often overlooked, producing minute fruiting bodies that are usually whitish, grey, or bluish in colour. Many species reproduce both sexually through spores and asexually through specialised structures, and they are found on substrates ranging from tree bark and dead wood to rocks and even moss. The genus has a cosmopolitan distribution, with species recorded from Europe, Australasia, the Americas, Africa, and oceanic islands. Several species are of interest to researchers studying how shifts between different substrates and reproductive strategies drive the formation of new species.
Micarea was circumscribed by Elias Magnus Fries in his 1825 work Systema Orbis Vegetabilis.[5] In his diagnosis , Fries characterised the genus by an effuse, crust-like thallus made up of aggregated gelatinous granules , together with free, almost spherical apothecia that are "always open" and lack a distinct margin. He recorded it from rocks and especially damp wood, and remarked that sterile material of Micarea prasina (the type species[6]) could be difficult to tell apart from algae-like crusts recognised at the time.[5]
There have been some taxonomic disputes about the genus.[7][8] Early molecular studies suggested that Micarea as traditionally circumscribed did not always form a single evolutionary lineage,[4] because some analyses placed other ectolechiaceous genera within Micarea when only one or a few gene regions were sampled. A large, five–locus phylogeny published in 2026 (based on worldwide sampling of 314 specimens representing 102 species) recovered Micarea in a broad sense as a single, moderately to strongly supported clade when some lineages historically treated as separate genera were included. In that analysis, Micarea formed the sister lineage to a predominantly tropical, foliicolous (leaf-dwelling) clade ("Ectolechiaceae sensu stricto") that includes genera such as Byssoloma, Calopadia, Fellhanera, Lasioloma and Sporopodium, although support for this relationship varied among analyses.[2]
On a classificatory level, that study favoured a middle-ground ("mesogeneric") solution rather than splitting the phylogeny into many small genera. It treated the earliest-diverging lineage (centred on Micarea crassipes and allies) as the separate genus Helocarpon, and retained the remaining clades in Micarea. It also reduced Szczawinskia to synonymy with Micarea (with new combinations for its species) and treated Uluguria as a synonym as well. The authors also discussed two small, potentially related genera. In their expanded sampling, Fellhaneropsis (including the type, F.myrtillicola) fell within the broader Micarea clade, but its placement and status were treated as unresolved because of missing data and limited sampling. Separate gene-tree analyses also suggested that Micareopsis irriguata may belong within the Micarea melanoprasina lineage, although this placement was treated as provisional pending additional data.[2]
The 2026 phylogeny also recovered multiple strongly supported infrageneric clades that often correlate with combinations of thallus structure, ascospore and conidial morphology, and pigment or secondary-chemistry profiles. The core M.prasina group (the clade containing the type species) is largely characterised by goniocyst -based thalli and by the restricted occurrence of micareic acid, methoxymicareic acid, and prasinic acid, whereas many of the more basal lineages lack detectable lichen substances and include a wider mix of thallus forms and photobiont types.[2]
Classification
The familial placement of Micarea has changed as classification systems have been revised. In morphology-based schemes the genus was long treated as the type of the family Micareaceae. Molecular phylogenetic work then showed that the "core" Micarealineage is closely allied to, and in single-locus analyses can intergrade with, a predominantly tropical group of foliicolous lichens that had often been treated as the separate family Pilocarpaceae; this led to proposals to merge Micareaceae into that broader family concept.[4]
Under current nomenclature, Pilocarpaceae is treated as an illegitimate name and Ectolechiaceae as the correct family name for this group, while Byssolomataceae (used in some databases) is treated as a later synonym. The 2026 multilocus revision adopted Ectolechiaceae for Micarea and recovered the genus as the sister lineage to a mainly foliicolous clade ("Ectolechiaceae sensu stricto") containing genera such as Byssoloma and Calopadia.[2][4]
Description
Species of Micarea are small crustose lichens whose thallus forms a thin, spreading crust that may sit on the surface or be partly immersed in the substrate. The thallus is commonly built from tiny, almost spherical granules called goniocysts (minute clusters of fungal hyphae wrapped around algal cells). These granules may remain distinct, merge into convex areoles, or form a cracked (rimose) or scurfy crust; in some species the areoles break down into soredia for asexual dispersal, while isidia are only rarely present. A distinct marginal prothallus is usually absent or inconspicuous, and the thallus typically lacks a true outer cortex , though some species develop a thin, colourless outer layer.[9]
Sexual fruiting bodies (apothecia) are usually present but are often minute (mostly under 1mm across). They are commonly whitish to grey or bluish, but may be brown to black, and they are not pruinose . The apothecia are typically immarginate and sit close to the thallus. Stalked forms occur only rarely, and a thallus-derived margin is absent in almost all cases. Internally, the apothecial margin ( exciple ) ranges from poorly developed to well developed and is formed from radiating, branched hyphae. The pigments in these tissues can give characteristic reactions in standard chemical tests, and the spore-bearing layer (hymenium) is gelatinised and may turn blue in iodine. The hymenium contains mostly branched paraphyses, though some species also have sturdier, unbranched paraphyses; the tips are not, or only slightly, swollen and lack a dark apical cap. The asci bear eight spores and are club-shaped, with apical structures that show characteristic staining patterns. Ascospores are colourless and smooth, lack a perispore , and may be simple or transversely septate. Their shapes range from ellipsoid and ovoid to spindle-shaped or needle-like. Asexual reproductive structures are usually pycnidia (rarely sporodochia ), which may be immersed, sessile, or raised on short stalks. Three conidium types are produced: macroconidia (often curved, thread-like, or coiled, and often septate), mesoconidia (shorter, usually aseptate, often with oil droplets, and mostly about 1–2μm wide), and microconidia (very small, simple, and to about 1μm wide). Chemically, many species have no detectable secondary metabolites by thin-layer chromatography, while others produce a range of substances. Gyrophoric acid occurs in several species.[9]
Reproduction
Lichen-forming fungi have developed diverse reproduction strategies. Genus Micarea is used as a model for studying how reproductive traits and environmental factors relate to speciation, because species differ in both substrate use and reproductive mode. Some Micarea species are generalists that can grow on several substrates, while others are restricted to narrow microhabitats. In the Micarea prasina group, some species are predominantly sexual, while others often lack sexual structures but bear numerous pycnidia that produce asexual conidia. The roles of the different conidium types are still not fully understood, but mesoconidia are thought to act as asexual propagules, based in part on specimens that regularly have only mesopycnidia and no apothecia. Recent phylogenetic analyses together with ancestral state reconstruction indicate that shifts in reproduction mode have evolved independently several times in the group, and that facultative and obligate lignicoles can be sister species. This pattern is consistent with a facultative lignicole ancestor, and suggests that shifts from bark to dead wood can coincide with a move towards asexual reproduction. One proposed explanation is that dead wood is a short-lived habitat, so species confined to it may need to colonise new suitable substrata quickly; faster dispersal via asexual propagules could then promote reproductive divergence and contribute to speciation.[10]
Species
As of February2026[update], Species Fungorum (in the Catalogue of Life) accepts 156 species of Micarea.[3] A major multilocus revision published in 2026 described four additional species (M.arthonioides, M.athromelaena, M.lignosorediata and M.regalis) and treated M.assimilata, M.crassipes, Micarea erratica and Micarea paratropa as belonging to Helocarpon rather than Micarea.[2]
1234Andersen, Heidi L.; Ekman, Stefan (2005). "Disintegration of the Micareaceae (lichenized Ascomycota): a molecular phylogeny based on mitochondrial rDNA sequences". Mycological Research. 109 (1): 21–30. doi:10.1017/S0953756204001625. PMID15736860.
12Fries, Elias M. (1825). Systema Orbis Vegetabilis (in Latin). Vol.1. Lund: Typographia Academica. pp.256–257.
↑Jørgensen, Per M. (1984). "Coppins, B. J. 1983. A taxonomic study of the lichen genus Micarea in Europe. – Bull". Nordic Journal of Botany. 4 (4): 544. doi:10.1111/j.1756-1051.1984.tb02061.x.
12345678910Coppins, B.J. (1983). "A taxonomic study of the lichen genus Micarea in Europe". Bulletin of the British Museum of Natural History. 11: 108.
1234Coppins, B. J.; Kantvilas, G. (2007). "Studies on Micarea in Australasia I. Four new species from Tasmania". The Lichenologist. 22 (3): 277–288. doi:10.1017/S0024282990000317.
↑Svensson, Måns; Thor, Göran (2011). "Micarea capitata, a new bryophilous lichen from Sweden". The Lichenologist. 43 (5): 401–405. doi:10.1017/S0024282911000338.
12345678910Kantvilas, Gintaras; Coppins, Brian J. (2019). "Studies on Micarea in Australasia II. A synopsis of the genus in Tasmania, with the description of ten new species". The Lichenologist. 51 (5): 431–481. doi:10.1017/S0024282919000343.
1234Coppins, Brian J.; Kashiwadani, Hiroyuki; Moon, Kwang Hee; Spribille, Toby; Thor, Göran (2021). "The genera Brianaria (Psoraceae) and Micarea(Pilocarpaceae) in Japan, with reports on other interesting species in Asia". The Lichenologist. 53 (1): 35–44. doi:10.1017/s0024282920000468.
1234Launis, A.; Pykälä, J.; van den Boom, P.; Sérusiaux, E.; Myllis, L. (2019). "Four new epiphytic species in the Micarea prasina group from Europe". The Lichenologist. 51 (1): 7–25. doi:10.1017/S0024282918000555. hdl:10138/326194.
12Coppins, B.J. (1995). "Two new, diminutive Micarea species from Western Europe". Bibliotheca Lichenologica. 58: 57–62.
123Launis, Annina; Malíček, Jiří; Svensson, Måns; Tsurykau, Andrei; Sérusiaux, Emmanuël; Myllys, Leena (2019). "Sharpening species boundaries in the Micarea prasina group, with a new circumscription of the type species M. prasina". Mycologia. 111 (4): 574–592. doi:10.1080/00275514.2019.1603044. hdl:10138/326192. PMID31099728.
↑Coppins, Brian J.; Aptroot, André (2008). "New species and combinations in The Lichens of the British Isles". The Lichenologist. 40 (5): 363–374. doi:10.1017/S0024282908008165.
↑van den Boom, Pieter P.G.; Sipman, Harrie J.M.; Divakar, Pradeep K.; Ertz, Damien (2017). "New or interesting records of lichens and lichenicolous fungi from Panama, with descriptions of ten new species". Sydowia. 69 (69): 47–72. doi:10.12905/0380.sydowia69-2017-0047.
123van den Boom, Pieter P.G.; Brand, A. Maarten; Coppins, Brian John; Sérusiaux, Emmanuel (2017). "Two new species in the Micarea prasina group from Western Europe". The Lichenologist. 49 (1): 13–25. doi:10.1017/S0024282916000633. hdl:2268/206810.
↑Poelt, J.; Döbbeler, P. (1975). "Über moosparasitische Arten der Flechtengattung Micarea und Vezdaea". Botanische Jahrbücher für Systematik, Pflanzengeschichte und Pflanzengeographie (in German). 96 (1–4): 328–352.
↑Czarnota, Paweł; Coppins, Brian J. (2005). "A second Micarea with a hypothecial K+ violet pigment". The Lichenologist. 37 (6): 477–479. doi:10.1017/S0024282905015318.
↑Rambold, G.; Triebel, D. (1992). "The inter-lecanoralean associations". Bibliotheca Lichenologica. 48: 169.
↑Coppins, B.J.; May, P.F. (2007). "Micarea neostipitata, a new species with pale stipitate pycnidia from eastern North America". The Lichenologist. 33 (6): 487–490. doi:10.1006/lich.2001.0350.
↑Zhurbenko, M.P. (2023). "Contributions to the knowledge of lichenicolous fungi growing on Sphaerophoraceae, with a key to the species". Herzogia. 36 (2): 504–523. doi:10.13158/heia.36.2.2023.504.
12Czarnota, P. (2007). "The lichen genus Micarea (Lecanorales, Ascomycota) in Poland". Polish Botanical Studies. 23: 174.
↑Fryday, A.M. (2004). "New species and records of lichenized fungi from Campbell Island and the Auckland Islands, New Zealand". Bibliotheca Lichenologica. 88: 127–146.
1234Kantelinen, Annina; Hyvärinen, Marko T.; Kirika, Paul; Myllys, Leena (2021). "Four new Micarea species from the montane cloud forests of Taita Hills, Kenya". The Lichenologist. 53 (1): 81–94. doi:10.1017/S0024282920000511. hdl:10138/329202.
↑Coppins, B.J.; James, P.W. (1979). "New or interesting British lichens IV". The Lichenologist. 11 (2): 139–179 [153]. doi:10.1017/s0024282979000190.
↑McCarthy, P.M.; Elix, J.A. (2020). "New species and new records of Micarea (Pilocarpaceae) from Australia". Australasian Lichenology. 87: 62–72.
↑McCarthy, P.M.; Elix, J.A. (2020). "A new species of Micarea (Pilocarpaceae) from soil in New Zealand". Australasian Lichenology. 87: 26–29.
↑Sérusiaux, E.; Coppins, B.J. (2009). "Micarea sipmanii, a new species with arbuscular pycnidia from the West Indies". Bibliotheca Lichenologica. 99: 367–372.
↑Coppins, B.J.; James, P.W. (2007). "New or interesting British lichens IV". The Lichenologist. 11 (2): 139–179. doi:10.1017/S0024282979000190.
↑Coppins, Brian J.; Spribille, Toby (2004). "Micarea subalpina Coppins & Spribille, a new subalpine species from the Rocky Mountains, USA". The Lichenologist. 36 (2): 97–102. doi:10.1017/S0024282904014070.
↑Boom, P.P.G. van den; Brand, A.M. (2004). "Micarea subcinerea, an additional species of the lichen flora from western Europe". Österreichische Zeitschrift für Pilzkunde. 13: 125–129.
↑Alstrup, V.; Christensen, S.N.; Hansen, E.S.; Svane, S. (1994). "The lichens of the Faroes". Fródskaparrit. 40: 61–121 [96].
12Aptroot, A. (2002). "New and interesting lichens and lichenicolous fungi in Brazil". Fungal Diversity. 9: 15–45.
↑Coppins, B.J. (1994). "Micarea submilliaria (Nyl.) Coppins, the correct name for Micarea subleprosula (Vezda) Vezda". Graphis Scripta. 6 (1): 37–38.
↑Kilias, H. (1981). "Revision gesteinbewohnender Sippen der Flechtengattung Catillaria Massal. in Europa (Lecanorales, Lecideaceae)". Herzogia (in German). 5 (3–4): 209–448. doi:10.1127/herzogia/5/1981/209.
↑Konoreva, Liudmila A.; Chesnokov, Sergey V.; Frolov, Ivan V. (2025). "Micarea svetlanae, a new species of the M. prasina group from the Russian Far East". The Lichenologist. 57 (1): 13–24. doi:10.1017/S0024282924000446.
↑Aptroot, André; Cáceres, Marcela Eugenia da Silva (2014). "New lichen species from termite nests in rainforest in Brazilian Rondônia and adjacent Amazonas". The Lichenologist. 46 (3): 365–372. doi:10.1017/s0024282913000340.
↑Du Rietz, G.E. (1923). "Lichenologiska fragment V. Nagra for Sverige nya eller foga kanda lavarter". Svensk Botanisk Tidskrift (in Swedish). 17: 83–95.
↑van den Boom, Pieter P.G.; Ertz, Damien (2014). "A new species of Micarea (Pilocarpaceae) from Madeira growing on Usnea". The Lichenologist. 46 (3): 295–301. doi:10.1017/S0024282913000698.
↑Coppins, B.J. (1985). "A new Micarea from the Scottish Highlands". The Lichenologist. 17 (1): 99–101. doi:10.1017/S002428298500010X.
↑CórdovaÇhávez, Octavio; Aptroot, André; Castillo-Campos, Gonzalo; Cáceres, Marcela E.S; Pérez-Pérez, Rosa Emilia (2014). "Three new lichen species from cloud forest in Veracruz, Mexico". Cryptogamie, Mycologie. 35 (2): 157–162. doi:10.7872/crym.v35.iss2.2014.157.
↑van den Boom, P.P.G.; Coppins, B.J. (2001). "Micarea viridileprosa sp. nov., an overlooked lichen species from western Europe". The Lichenologist. 33 (2): 87–91. doi:10.1006/lich.2000.0310.
↑Muhr, L.E. (1987). "Lavfloran i Gravbficksravinen i Vfirmland". Svensk Botanisk Tidskrift (in Swedish). 81 (1): 17–35.
↑Coppins, B.J.; Tønsberg, T. (2001). "A new xanthone-containing Micarea from northwest Europe and the Pacific Northwest of North America". The Lichenologist. 33 (2): 93–96. doi:10.1006/lich.2000.0311.
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