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Lepraria xerophila Tønsberg |
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Nomenclatural data
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Lichen Flora of the Greater Sonoran Desert Region 2: 326 (2004); type: Mexico, Baja California, Punta Santo Tomas, 31°33’30”N, 116°40’50”W, 30. Dec. 1995, T. H. Nash 38224 (ASU—holotypus; BG, DUKE—isotypi).
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Morphology
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Thallus crustose to subfoliose or squamulose, with membranous, slightly granular appearance; whitish grey to pale yellowish grey; usually thick, relatively hard; shape rosettes, later irregular patches, rosettes to 2 cm, irregular patches to 10 or more cm in diam.; margin delimited, obscurely to distinctly lobed, rarely placodioid, with marginal rim up to 0.5 mm thick; subcorticate patches may be present; medulla usually present, distinct in thick specimens, white; hypothallus absent, lower surface whitish grey, without tomentum; prothallus absent; areoles absent; marginal lobes can be squamulose; large thallus surfaces without soredia usually present, soredia few or absent; large granules or lobules similar to isidia present, numerous, shape regular to irregular, sometimes capitate, easily detached, acting as diaspores; morphologically variable, differentiated algal layer beneath upper surface present. Photobiont green, aggregated in globose groups 24-50 µm in diam.
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Chemistry
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This species comprises 2 chemotypes. Common (1): pannaric acid 6-methylester, rangiformic and/or roccellic acid; atranorin (minor to trace), methyl porphyrilate ± (minor to trace), porphyrilic acid ± (trace), pannaric acid ± (trace), unknown dibenzofuran (trace); K–, C–, KC–, Pd– or + orange. Rare (2): norascomatic acid, strepsilin (minor to trace), isostrepsilic acid (minor to trace), atranorin (minor to trace), chloratranorin (minor to trace); K– or + pale yellow, C– or + pale yellow, KC– or + green becoming brown, Pd–.
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Remarks
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Discussion. According to molecular studies belongs to a monophyletic group together with L. membranacea, L. vouauxii, L. xerophila, L. bergensis, L. isidiata, L. santosii (Crespo et al. 2006), see the discussion under L. membranacea. Species containing pannaric acid 6-methylester as major substance include L. impossibilis, L. sipmaniana, L. vouauxii, L. xerophila, see the discussion under L. vouauxii. Species producing isidia-like structures include L. crassissima, L. isidiata, L. santosii, L. xerophila, see the discussion under L. isidiata. Several species can develop well developed lobes, see the discussion under L. membranacea.
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Ecology and distribution
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Substrate and ecology: soil, rarely rock or wood; dry places. Distribution: Europe, North America, arid areas.
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