Acanthothecis is a genus of lichen-forming fungi in the family Graphidaceae.[1] The genus was circumscribed by Frederick Edward Clements in 1909.[2] These lichens form pale grey-brown to olive-green crusts on tree bark and are characterized by elongated, pencil-like slits containing spores, with distinctive tiny spines on internal filaments that help distinguish them from similar genera. The genus includes about 50 species found primarily in tropical and subtropical forests worldwide, where they grow on living tree bark and serve as indicators of relatively undisturbed woodland environments.
Description
Acanthothecis forms a pale grey-brown to olive-green crust (thallus) that may lack a skin (cortex) or bear a thin one, and often contains scattered crystals that give a slightly granular texture. Its fruit bodies are lirellae—elongated, pencil-like slits—ranging from immersed to sitting on the surface; their lips are usually well developed and can be smooth or faintly striate. The rim that encircles each lirella (excipulum) is generally colourless rather than the charcoal-black seen in many relatives, and it houses minute filaments (periphysoids and paraphyses) whose tips are armed with tiny spines—an unusual diagnostic trait in the family. Inside, the hymenium (spore-bearing layer) does not stain blue in iodine tests (non-amyloid) and is usually clear, while the asci are of the Graphis-type and release two to eight hyaline ascospores that are distoseptate—divided by thin inner walls that give each compartment a lens-shaped outline—and typically show no iodine reaction (I–).[3]
Morphologically the genus clusters into three informal groups. A. obscura has a dark brown excipulum and an inspersed (grainy) hymenium; the A. hololeucoides group features a grey to pale yellowish thallus with mainly smooth lirellae; and the A. subclavulifera group shows an olive thallus with conspicuously striate lips. The combination of spinulose filaments, predominantly non-carbonised rim, and I– spores separates Acanthothecis from superficially similar genera such as Anomalographis, Anomomorpha, Fissurina, Gymnographopsis and Hemithecium, all of which lack one or more of these features.[3]
Ecology
Acanthothecis occurs across the humid to seasonally dry tropics and subtropics worldwide. They are predominantly corticolous, growing on the bark of living trees in primary or only lightly disturbed evergreen forests, where they tolerate both shaded and moderately exposed microhabitats. Because the genus favours intact forest canopies, several species are considered indicators of relatively undisturbed woodland and may decline with intensive logging or land conversion.[3]
^Herrera-Campos, María de los Ángeles; Barcenas-Peña, Alejandrina; Miranda-González, Ricardo; Mejía, Maricarmen Altamirano; González, Joshua A. Bautista; Colín, Paola Martínez; Téllez, Norberto Sánchez; Lücking, Robert (2019). "New lichenized Arthoniales and Ostropales from Mexican seasonally dry tropical forest". The Bryologist. 122 (1): 62–83. doi:10.1639/0007-2745-122.1.062.
^Archer, A.W.; Elix, J.A. (2008). "Three new species in the Australian Graphidaceae (lichenized Ascomycota)". Australasian Lichenology. 63: 26–29.
^ abcSharma, Bharati; Makhija, Urmila; Khadilkar, Pradnya (2010). "New species and records of the lichen genus Acanthothecis (Graphidaceae) from India". The Lichenologist. 42 (5): 547–555. doi:10.1017/s0024282910000253.
^ abcdefghijklmnFeuerstein, Shirley Cunha; Aptroot, André; da Silveira, Rosa Mara Borges; Lücking, Robert; Cáceres, Marcela Eugenia da Silva (2022). "An updated world key to the species of Acanthothecis s. lat. (Ascomycota: Graphidaceae), with ten new species from Brazil". The Lichenologist. 54 (2): 87–99. doi:10.1017/s0024282922000019.
^Archer, A.W.; Elix, J.A. (2007). "Two new species in the Australian Graphidaceae (lichenized Ascomycotina)". Australasian Lichenology. 61: 18–20.
^Makhija, Urmila; Adawadkar, Bharati (2007). "Trans-septate species of Acanthothecis and Fissurina from India". The Lichenologist. 39 (2): 165–185. doi:10.1017/s0024282907004756.
^ abcLendemer, J.C.; Harris, R.C. (2014). "Seven new species of Graphidaceae (Lichenized Ascomycetes) from the Coastal Plain of southeastern North America". Phytotaxa. 189 (1): 153–175. doi:10.11646/phytotaxa.189.1.11.
^Muscavitch, Zachary M.; Lendemer, James C. (2016). "A new species of Acanthothecis (Ostropales), highlights subtropical floristic elements of the southern Appalachian lichen biota in eastern North America". The Bryologist. 119 (4): 350–360. doi:10.1639/0007-2745-119.4.350.
^ abvan den Boom, Pieter P.G.; Sipman, Harrie J.M. (2013). "Sixty-two species of lirelliform Graphidaceae (Ascomycota) new to Panama, with four species newly described to science". Herzogia. 26: 9–20. doi:10.13158/heia.26.1.2013.9.
^Makhija, U.; Adawadkar, B. (2003). "A new species of Acanthothecis from India". Mycotaxon. 88: 139–141.
^Gupta, P.; Sinha, G.P. (2015). "A new species of Acanthothecis (lichenized Ascomycetes) from India". Journal on New Biological Reports. 4 (2): 98–102.
^ abJoshi, Santosh; Upreti, Dalip K.; Thanh, Nguyen Thi; Nguyen, Anh Dong; Hur, Jae-Seoun (2017). "New and interesting species in the family Graphidaceae (Ascomycota: Ostropales) from Vietnam". The Lichenologist. 49 (3): 259–268. doi:10.1017/s0024282917000172.
^Kantvilas, G. (2010). "Acanthothecis virgulicola, a new Tasmanian lichen". Herzogia. 23 (1): 9–13. doi:10.13158/heia.23.1.2010.9.
