Most lichens are a
symbiosis between an
ascomycetefungus and a photosynthetic
green alga. However, a small percentage of lichens (approximately 10%) are
cyanolichens and contain a photosynthetic
cyanobacterium instead of green algae,[2] and an even smaller number (less than 1%) are
basidiolichens and contain a
basidiomycete fungus instead of an ascomycete.[3] This makes Dictyonema more closely related to
mushrooms than it is to most other lichens.
Taxonomy and naming
The genus Dictyonema was first named in 1822 by
Carl Agardh and
Carl Kunth after examining a novel fungus that was sent to them from Brazil.[4] The genus was redefined in 1978 when
Erast Parmasto assessed 40 different species of basidiolichens that were previously divided into 3 families and 8 genera (including Cora, Dichonema, Laudatea, Rhipidonema, and Thelephora), and reduced them to 5 species in the single genus Dictyonema.[5] This resulted in a rather diverse group of lichens that has since grown in size to more than 20 species.[3] There is, however, some recent debate over whether or not all of these species should be included in the same genus.[6]
Species
A recent (2020) estimate placed 28 species in Dictyonema.[7]
Dictyonema is a diverse group of lichens. There are species of a variety of different shapes, including
foliose,
crustose, and
filamentous.[3] Most species grow on soil, rock,[15] moss,[16] or rotting logs,[17] but one species
grows on the leaves of trees.[3] Although species of Dictyonema are mainly tropical, they range from the tropical lowlands to an elevation of 4,300 m (14,100 ft) in the Andes.[15]
Evolutionary relationships and lichenization
The Dictyonema fungus is a
basidiomycete, so it developed
lichenization independently from the
ascomycete lichens.[18] Within the basidiomycetes, Dictyonema is closely related to three other genera of basidiolichens that are also in the family
Hygrophoraceae: Lichenomphalia, Acantholichen, and Cyphellostereum.[3] The
molecular data indicates that lichenization has evolved independently at least twice, and perhaps three times, within these four genera, which suggests that for some reason the fungi in Hygrophoraceae are predisposed to evolve into lichens.[3] The majority of the other, non-lichenized fungi in this family are
saprotrophic (consuming decaying organic matter) or
ectomycorrhizal (symbiotic with plant roots), although numerous species, such as Arrhenia, grow on mosses and derive nutrition from them.[3][19] It is not yet understood why these fungi are more inclined to become lichens.[3]
^Ertz, Damien; Lawrey, James D.; Sikaroodi, Masoumeh; Gillevet, Patrick M.; Fischer, Eberhard; Killmann, Dorothee; Sérusiaux, Emmanuël (2008). "A new lineage of lichenized basidiomycetes inferred from a two-gene phylogeny: The Lepidostromataceae with three species from the tropics". American Journal of Botany. 95 (12): 1548–1556.
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10.3732/ajb.0800232.
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^Hawksworth, DL, PM Kirk, BC Sutton, and DN Pegler. 1995. Dictionary of the fungi. CAB, Wallingford
^
abcdefghLawrey, James D.; Lücking, Robert; Sipman, Harrie J.M.; Chaves, José L.; Redhead, Scott A.; Bungartz, Frank; Sikaroodi, Masoumeh; Gillevet, Patrick M. (2009). "High concentration of basidiolichens in a single family of agaricoid mushrooms (Basidiomycota: Agaricales: Hygrophoraceae)". Mycological Research. 113 (10): 1154–1171.
doi:
10.1016/j.mycres.2009.07.016.
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^Kunth, CS, and CA Agardh. 1822. Synopsis Plantarum, Quas in Itinere ad Plagam Aequinoctialem Orbis Novi, Collegerunt Al. de Humboldt et Am. Bonpland (Paris). Volume 1, pg. 1.
^Parmasto, E. (1978). "The genus Dictyonema ('Thelephorolichenes')". Nova Hedwigia. 29: 99–144.
^Luis Chaves, José; Lücking, Robert; Sipman, Harrie J.M.; Umaña, Loengrin; Navarro, Enia (2004). "A First Assessment of the Ticolichen Biodiversity Inventory in Costa Rica: The Genus Dictyonema (Polyporales: Atheliaceae)". The Bryologist. 107 (2): 242–249.
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^
abcLücking, Robert; Dal-Forno, Manuela; Wilk, Karina; Lawrey, James D. (2013). "Three new species of Dictyonema (lichenized Basidiomycota: Hygrophoraceae) from Bolivia". Acta Nova. 6: 4–16.
^
abcdDal Forno, Manuela; Bungartz, Frank; Yánez-Ayabaca, Alba; Lücking, Robert; Lawrey, James D. (2017). "High levels of endemism among Galapagos basidiolichens". Fungal Diversity. 85 (1): 45–73.
doi:
10.1007/s13225-017-0380-6.
S2CID32287424.
^Lücking, Robert; Barrie, Fred R.; Genney, David (2014). "Dictyonema coppinsii, a new name for the European species known as Dictyonema interruptum (Basidiomycota: Agaricales: Hygrophoraceae), with a validation of its photobiont Rhizonema (Cyanoprokaryota: Nostocales: Rhizonemataceae)". The Lichenologist. 46 (3): 261–267.
doi:
10.1017/s0024282913000352.
S2CID85215183.
^Schmull M, Dal-Forno M, Lücking R, Cao S, Clardy J, Lawrey JD (2014). "Dictyonema huaorani (Agaricales: Hygrophoraceae), a new lichenized basidiomycete from Amazonian Ecuador with presumed hallucinogenic properties". The Bryologist. 117 (4): 386–94.
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^Yánez, Alba; Dal-Forno, Manuela; Bungartz, Frank; Lücking, Robert; Lawrey, James D. (2011). "A first assessment of Galapagos basidiolichens". Fungal Diversity. 52 (1): 225–244.
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10.1007/s13225-011-0133-x.
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^
abLarcher, W.; Vareschi, V. (1988). "Variation in morphology and functional traits of Dictyonema glabratum from contrasting habitats in the Venezuelan Andes". The Lichenologist. 20 (3): 269–277.
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^Plitt, Charles C. (1921). "A preliminary report, with notes, on the lichens Found near the Cinchona Botanical Station, Jamaica, British West Indies". The Bryologist. 24 (4): 60–64.
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^Gargas, Andrea; DePriest, Paula T.; Grube, Martin; Tehler, Anders (1995). "Multiple origins of lichen symbioses in fungi suggested by SSU rDNA phylogeny". Science. 268 (5216): 1492–1495.
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