Lepraria xanthonica Lendemer
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Authority
Lendemer, James C. 2010. Notes on Lepraria s.l. (Lecanoromycetes, Ascomycota) in North America: New species, new reports, and preliminary keys. Brittonia. 62 (3): 267-292.
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Family
Stereocaulaceae
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Scientific Name
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Description
Description - Thallus crustose, leprose, without "lobes," diffuse, patchy to convergent and continuous, with granules initially sparse distributed, eventually accumulating in over- lapping heaps that become confluent to form a thin continuous crust (0.2-0.4(-0.5) mm thick), dull greenish-gray in color; hypothallus a thin network of hyphae underneath the granules and extending outward from the edge of the thallus; hyphae anchoring the granules to each other and to the substrate, 2-3 um wide, hyaline, obscurely septate, frequently branching at the septa, thin walled, obscured by a layer of crystals that dissolve in KOH; rhizohyphae absent; granules medium in size (25-)30- 40 jum in diameter; ecorticate, round, usually a single layer of hyphae surrounding an algal core consisting of <10 large photobiont cells, readily dividing; photobiont green, coccoid, cells globose, (9-) 12- 15 urn in diameter.
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Discussion
Chemistry. - TLC: usnic acid, zeorin, 5,7- dichloro-3-O-methylnorlichexanthone, 3-0- methylasemone. HPLC (performed on the holotype and three paratypes cited below): usnic acid (major), [zeorin, not detectable by HPLC but confirmed by TLC], 5,7-dichloro-3-O-methylnorlichexanthone (submajor), 3-O-methyla- semone (minor). Spot tests: K-, C-, KC+ yellow-orange, UV+ dull yellowish-orange, Dirnroths solution^. Etymology. - The specific QpiûiQtxanthonica denotes the unusual chemistry of the species.
Ecology and distribution. - Based on the available material Lepraria xanthonica is widespread in temperate eastern North America with disjunct populations in the Ozarks. It primarily occurs on shaded non-calcareous rocks in humid habitats, particularly over- hangs, although the type collection is from weakly calcareous shale. In extremely humid habitats the species also occasionally occurs on the bases of hardwood trees.
Discussion. - Lepraria xanthonica is one of two species in the genus known to produce xanthones. In this respect L. disjuncta, also described herein, is most similar to the new species. That taxon differs from L. xanthonica in producing a different set of xanthones as well as usnic acid, being restricted primarily to calcareous rock outcrops, and in having a thicker thallus with larger granules. Although many species of Lepraria occur on rock in humid microhabitats, only a few are morphologically comparable to L. xan- thonica in having a thin thallus composed of aggregations of granules. These species are easily distinguished with the application of spot test reagents in the key provided at the beginning of this section.