Overview

Brief Summary

Description

 Thallus: usually not evident as a distinct structure, but basidiomata originating from tangled hyphae which in some species form a dark greenish, crust-like growth that may be visible even when basidiomata are absent; Basidiomata: "crustose" (forming a matt-like cover of appressed or erect branched fibrils) to "foliose", often forming semicircular brackets, which are sessile, standing out from the substrate, or resupinate (partly attached, partly lifted up and bent backwards), single or united in rosettes, soft or paper-like, small or to 20 (-25) cm diam.; upper surface: blue- to gray-green, gray to dark or olive green, or whitish or yellowish, often with concentric markings, sometimes unevenly thickened or sulcate (grooved) or zoned, smooth to frequently roughened, or becoming villose, hispid or fibrillose (appearing "combed" hairy or shaggy) due to irregularly to radially arranged filaments of the photobiont; photobiont: primary one a cyanobacterium (Scytonema or sometimes Chroococcus or similar genera), secondary photobiont absent, usually in a well-developed layer in the basidiomata, the filaments surrounded by a coating of longitudinally arranged hyphae; lower surface: smooth and even, to warty or granular, without gills or pores; hymenophores (hymenium-bearing parts) soon or eventually produced, scattered to reticulate or forming low concentric bands, dehiscent, white, cream or buff, smooth to ± tomentose, continuous or broken up; basidiomata anatomy: with monomitic hyphal system, consisting only of diploid (dikaryotic) generative hyphae (giving rise to other hyphal types and to the hymenium) which are thin- to thick-walled, hyaline or yellowish, septate, irregularly branched or at times dichotomous, with or without clamp connections , 3-11 (-13) µm diam.; without sterile bodies (cystidia and gleocystidia); hymenium organized into an irregular but definite palisade layer with thick increments of basidia and basidioles (immature basidia); basidia: in bundles, clavate or subcylindrical, not constricted, 15-30 x 5-9 µm, bearing four slender, slightly curved sterigmata (spore-producing structures); basidiospores: simple, hyaline or yellowish brown, ellipsoid to subcylindrical or almost boat-shaped, smooth, I-, 6-10 x 2.8-5 µm, thin-walled, non-amyloid; Secondary metabolites: none detected; Geography: mostly tropical or subtropical, but some species occurring in boreal-temperate areas; Substrate: trees, mossy rocks and soil.; Notes: Although this genus lacks a true thallus (in the sense of a distinctly developed "vegetative plant body"), some authors have referred to the basidioma, which contains the photobiont, as being the thallus. 
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Source: Lichen Flora of the Greater Sonoran Desert Region

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Dictyonema

For the genus of graptolites also called Dictyonema, see Graptolithinia.

Dictyonema is a large and diverse genus of mainly tropical basidiolichens in the family Hygrophoraceae.[1]

The Dictyonema symbiosis[edit]

Most lichens are a symbiosis between an ascomycete fungi and a photosynthetic green algae. However, a small percentage of lichens (approximately 10%) are cyanolichens and contain a photosynthetic cyanobacteria instead of green algae,[2] and an even smaller number (less than 1%) are basidiolichens and contain a basidiomycete fungi instead of an ascomycete.[3] Dictyonema is a symbiosis between a basidiomycete fungi and a scytonematoid cyanobacteria, making it both a basidiolichen and a cyanolichen, which is a very rare combination.[4] This makes Dictyonema more closely related to mushrooms than it is to most other lichens.

Taxonomy and naming[edit]

The genus Dictyonema was first named in 1822 by Carl Adgardh and Carl Kunth after examining a novel fungus that was sent to them from Brazil.[5] 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.[6] This resulted in a rather diverse group of lichens that has since grown in size to more than 20 species, making Dictyonema the largest genus of basidiolichen.[4] There is, however, some recent debate over whether or not all of these species should be included in the same genus.[4][7]

Species[edit]

Morphology and ecology[edit]

Dictyonema is a diverse group of lichens. There are species of a variety of different shapes, including foliose, crustose, and filamentous.[4] Most species grow on a soil, rock,[8] moss,[9] or rotting logs,[10] but one species grows on the leaves of trees.[4] Although species of Dictyonema are mainly tropical, they range from the tropical lowlands to an elevation of 4300 m in the Andes.[8]

Evolutionary relationships and lichenization[edit]

The Dictyonema fungus is a basidiomycete, so it discovered lichenization independently from the ascomycete lichens.[11] Within the basidiomycetes, Dictyonema is closely related to three other genera of basidiolichens that are also in the family Hygrophoraceae: Lichenomphalia, Acantholichen, and Cyphellostereum.[4] Interestingly, 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.[4] 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.[4][12] It is not yet understood why these fungi are more inclined to become lichens.[4]

Traditional use by people[edit]

An unidentified species of Dictyonema, possibly Dictyonema sericeum, is called nenendape by the Huaorani of Amazon jungle of Ecuador. An infusion is made with this lichen that causes intense hallucinations, and it is used by the shaman to call upon malevolent spirits to curse people. It is also used to cause sterility.[13]

See also[edit]

References[edit]

  1. ^ Ertz, D., J. D. Lawrey, M. Sikaroodi, P. M. Gillevet, E. Fischer, D. Killmann, and E. Sérusiaux. 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.
  2. ^ Hawksworth, DL, PM Kirk, BC Sutton, and DN Pegler. 1995. Dictionary of the fungi. CAB, Wallingford
  3. ^ Lawrey, JD, M Binder, P Diederich, MC Molina, M Sikaroodi, and D Ertz. 2007. Phylogenetic diversity of lichen-associated homobasidiomycetes. Molecular Phylogenetics and Evolution 44: 778–789.
  4. ^ a b c d e f g h i James D. Lawrey, JD, R Lücking, HJM Sipman, JL Chaves, SA Redhead, F Bungartz, M Sikaroodi, and PM Gillevet. 2009. High concentration of basidiolichens in a single family of agaricoid mushrooms (Basidiomycota: Agaricales: Hygrophoraceae). Mycological Research 113: 1154-1171.
  5. ^ 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.
  6. ^ Parmasto E, 1978. The genus Dictyonema ('Thelephorolichenes'). Nova Hedwigia 29: 99–144.
  7. ^ Jose Luis Chaves, JL, R Lücking, HJM Sipman, L Umaña, and E Navarro. 2004. A first assessment of the Ticolichen Biodiversity Inventory in Costa Rica: The genus Dictyonema (Polyporales: Atheliaceae). The Bryologist 107(2): 242-249.
  8. ^ a b Larcher, W, and V Vareschij. 1988. Variation in morphology and functional traits of Dictyonema glabratum from contrasting habitats in the Venezuelan Andes. Lichenologist 20(3): 269-277.
  9. ^ Coppins, BJ, and PW James. 1979. A British species of Dictyonema. Lichenologist 11(1): 103-108.
  10. ^ Plitt, CC. 1921. A preliminary report, with notes, on the lichens found near the Cinlhona Botanical Station, Jamaica, British West Indies. The Bryologist 24(5): 70-74.
  11. ^ Gargas, A., P. T. DePriest, M. Grube, and A. Tehler. 1995. Multiple origins of lichen symbioses in fungi suggested by SSU rDNA phylogeny. Science 268(5216): 1492-1495.
  12. ^ Döbbeler, P. 1997. Biodiversity of bryophilous ascomycetes. Biodiversity and Conservation 6: 721-738.
  13. ^ Davis, E. W. and J. A. Yost. 1983. Novel hallucinogens from eastern Ecuador. Botanical Museum Leaflets [Harvard University] 29(3): 291-295.
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