Lepraria disjuncta Lendemer

  • Authority

    Lendemer, James C. 2010. Notes on s. l. (Lecanoromycetes, Ascomycota) in North America: New species, new reports, and preliminary keys. Brittonia. 62 (3): 267-292.

  • Family

    Stereocaulaceae

  • Scientific Name

    Lepraria disjuncta Lendemer

  • Description

    Description - Thallus crustose, leprose, lacking marginal "lobes," continuous but not distinctly bi-layered, forming small discrete thalli which expand marginally and often overlap, become confluent, and form a thin (0.3-0.5 mm) but well developed crust, very light green-white in color and often with a distinctive yellowish hue; hypothallus a poorly developed network of loosely inter- twined hyphae inspersed with large crystals of calcium oxalate[?] surrounding the gran- ules and projecting outward from the edge of the thallus/granules; hyphae 2-4 um wide, hyaline, distinctly septate, frequently branch- ing at the septa, thick walled, obscured by a thick layer of crystals that dissolve in KOH; rhizohyphae absent; granules large, (70-)80- 100(-130)um in diameter, ecorticate or with a thin pseudocortex of one to several layers of gelatinized hyphae, globose and discrete, readily dividing; photobiont green, coccoid, cells globose, (10- )12- 15 jum in diameter.

  • Discussion

    Chemistry. - Specimens analyzed with TLC and spot tests were found to consistently produce usnic acid as the major substance along zeorin and two xanthones as accessories. Additional spots which resemble triterpenes are often found with TLC but these may belong to contaminants. The spot tests that would normally detect thiophanic acid and/or arthothelin are variable in this taxon, and it may be because they are present in low concentrations. Further, the positive KC reaction which would confirm the presence of these xanthones can be masked by the positive reaction of usnic acid (which is KC+ yellow- gold).

    TLC: Usnic acid, zeorin, thiophanic acid, arthothelin, traces of other unidentified substances.

    HPLC (performed on specimens cited below denoted by "HPLC!"): usnic acid (major), thiophanic acid (major or minor), arthothelin (major or minor), and [zeorin, not detectable in HPLC analysis but confirmed with TLC]. Spot tests: K-, C±weak yellow, KC+ strong yellow to yellow-orange, UV- or UV+ faint dark reddish- orange, Dimroths solution+.

    Entymology - - The specific epithet disjuncta relates to the geographic distribution of the species which has disjunct populations in the Ozark Ecoregion, Great Lakes, and southeast.

    Ecology and distribution. - Like many other saxicolous Lepraria species L. disjuncta is most often found in cool moist rock overhangs or other high humidity habitats with low light intensities. The species is ecologically distinctive in occurring primarily on strongly calcareous rocks such as pure limestone or dolomite. Occasional populations have been found on semi-calcareous substrates (e.g., sandstones with a calcareous binding, or calcareous shales) and one large population was found growing on bryophyte mats over weakly calcareous shale.

    Presently the species is known from numerous scattered occurrences in eastern and central North America. It is likely the disjunct pattern of its geographic distribution is due largely to the limited availability of calcareous substrates in the region.

    Discussion. - Lepraria disjuneta is one of the two species in genus known to produce xanthones (both are described here). The other species, L. xanthonica, is apparently very rare, produces a different set of xanthones, and has a thinner more dispersed thallus It is noteworthy that Lepraria disjuneta is seemingly restricted to calcareous substrates. In North America the only other Lepraria species I have observed on such substrates is the ubiquitous L. lobificans auct. (the type collection of L.finkii (de Lesd.) R.C. Harris, a synonym of L. lobificans auct., was found on limestone). Lepraria lobificans auct. is mor- phologically similar to the new species but has a well developed hypothallus and differs chemically in producing atranorin, zeorin, and stictic acid (KC-, P+ orange).

    In the field the yellowish color and rela- tively thick thallus of Lepraria disjuneta can also lead to confusion with L. vouauxii (Hue) R.C. Harris. That species is readily distin- guished from L. disjuneta by the absence of usnic acid and the presence of other dibenzo- furans instead of xanthones (the thallus is KC-, P-).

    Another leprose crustose lichen that occurs on calcareous rocks is Lecanora rouxii S. Ekman & Tonsberg which was originally described as Lepraria flaves cens Clauzade & Cl. Roux ex Cl. Roux & Tonsberg (Tonsberg, 2002) because it is typically sterile and has a leprose thallus. Lecanora rouxii is known only from Europe and produces atranorin and chromones (e.g., sordidone) rather than usnic acid and xanthones (Tonsberg, 2002). Although originally described in the genus Lepraria the species was transferred to Lecanora Ach. on the basis of molecular data (Grube et al., 2004). Generic placement in Lecanora was subsequently confirmed by the discovery of a specimen with apothecia (Kukwa & Diederich, 2007).