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Lepraria membranacea (Dicks.) Vain. |
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Nomenclatural data
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Acta Soc. Fauna Flora Fennica 49(2): 265 (1921); type: United Kingdom, Scotland, J. Dickson (BM ex K ex D Turner—holotypus). Lichen membranaceus Dicks., Fasc. Pl. Crypt. Brit. 2: 21 (1790).—Leproloma membranaceum (Dicks.) Vain., Term. Füz. 22: 293 (1899).
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Morphology
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Thallus crustose to subfoliose, leprose, with membranous appearance; whitish or greyish yellow to pale yellowish green to light green; usually tightly attached to the substrate at centre, loosely at margins; shape more or less rounded patches, often becoming fused with other thalli, up to 5 cm in diam.; margin delimited, lobes present, well developed, rounded, wide, margin raised or flat; cortex absent; medulla present, distinct, white; hypothallus present, usually well developed, brown to greyish black, sometimes white along margin, usually forming thick tomentum; prothallus absent; areoles absent; squamules absent; thallus surfaces without soredia sometimes present, soredia abundant, sometimes not well separated at margin, fine to medium, up to c. 100 µm in diam.; wall indistinct to distinct; projecting hyphae sometimes present, short; consoredia often present, up to c. 200 µm; isidia-like structures absent. Photobiont green, coccoid, up to 15 µm in diam.
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Chemistry
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Pannaric acid (major) with satellite dibenzofurans (minors to traces), roccellic/angardianic (rarely absent), atranorin ± (major to trace); very rarely norstictic acid or zeorin have been found (Baruffo et al. 2006, Laundon 1989). K– or + yellow, C–, Pd+ reddish orange.
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Remarks
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According to molecular studies L. membranacea, L. vouauxii, L. xerophila, L. bergensis, L. isidiata, L. santosii form a monophyletic group in Lepraria based on ITS (Crespo et al. 2006), these species also may all be membranous and lobed (L. vouauxii only rarely develops small lobes).
L. membranacea is the oldest name and the most widely distributed species of the strongly lobate Leprarias. L. bergensis, L. membranacea, L. normandinoides, L. sipmaniana are morphologically quite similar, see the discussion under L. bergensis. Species that can form prominent lobes include L. atrotomentosa, L. bergensis, L. coriensis, L. impossibilis, L. isidiata, L. lobata, L. membranacea, L. normandinoides, L. pallida, L. santosii, L. sipmaniana, L. squamatica (rarely), L. xerophila. All these species are relatively easily distinguishable using chemical and morphological characters, except perhaps L. lobata and L. pallida in some cases (see the discussion under these species). Differences are as follows: L. atrotomentosa contains lecanoric acid, atranorin and zeorin and has a well developed layer of dark hyphae on the lower side of thallus. L. bergensis produces anthraquinones and is relatively small. L. coriensis contains usnic acid and zeorin. L. impossibilis produces lecanoric and pannaric acid. L. isidiata can produce fumarprotocetraric and protocetraric acids, isidia-like structures together with coarse soredia. L. lobata and L. pallida produce atranorin, zeorin and fatty acids (see the discussion under these species). L. membranacea produces pannaric acid and is relatively large. L. normandinoides produces protocetraric and/or fumarprotocetraric acids (very rarely only atranorin and roccellic acid), lacks isidia-like structures, soredia fine. L. santosii produces stictic acid complex, isidia-like structures together with coarse soredia. L. sipmaniana pannaric acid 6-methylester, lacks isidia-like structures, soredia variably sized, thallus colour usually relatively brightly yellowish. L. squamatica contains squamatic acid. L. xerophila produces pannaric acid 6-methylester or norascomatic acid, has isidia-like structures (lobules) and few or no soredia.
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Ecology and distribution
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Substrate and ecology: mainly rock and mosses on rock, rarely bark or soil; shaded to sun-exposed, sheltered from rain. Distribution: worldwide but scattered.
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