Physcia alba (Fée) Müll. Arg.

Data Set Maintenance: Data set compiled (Sonoran Desert Lichen Flora). Data set author(s): Bungartz F. (02-01-20) @EXCL@ Esslinger T. @EXCL@ Nash T.H. Data set reviewer(s): Nash T.H.; to be published after submission; February 2002.

Nomenclature: Current taxonomic status: accepted. Taxonomic rank: species. Currently accepted name Physcia alba (Fée) Müll. Arg. Physcia. Physciaceae Zahlbr. (1898); Lecanorineae; Lecanorales.

Type Information: Basionym: Parmelia alba Fée. Type: Physciua alba (Fée) Müll. Arg.

Biogeography: Neotropical. Continent: Northern America and Southern America. Checklist records: Mexico and Sonoran Desert.

Ecology: Biotroph; lichenized; lignicolous, corticolous, or sometimes saxicolous (in more or less exposed sites); episubstratic; growing sun-exposed or partially shaded; under conditions which are dry or moist.

Thallus: Foliose, subdivided into main parts, continuous throughout, lobed; lobes linear, horizontal; angular at the front; concave or plane; sometimes imbricate. Thallus Size and Differentiation: Small; apex curved upwards; truncate. Thallus Outline: Sometimes irregular or orbicular; margin up-turned; soon disappearing. Upper Surface: White or pale grey (to cream), matt, smooth; occasionally maculate; maculae irregular (maculae generally weakly developed); epruinose; eciliate; without hairs; not isidate; not sorediate; not blastidiate; not schizidiate; not lobulate. Lower Surface: Present, grey (pale graphite) or white, loosely attached attached; attached by holdfasts; rhizinate; rhizines grey (pale graphite) or white.

Upper Cortex: Present; outer cortical layer paraplectenchymatous; inner cortical layer prosoplectenchymatous (in lower parts with isodiametric cells). Medulla: White. Lower Cortex: Present.

Reproduction Strategy: With sexual (and possible asexual) stages. Ascocarps: Orbicular, soon sessile or substipitate, abundant, small. Margin: Lecanorine, smooth, persistent, prominent; not isidiate; not ciliate; not hirsute. Disk: Plane; black or brown; rarely pruinose, pruina scarce, white. Epithecium: Apical cells spathulate (only capitate, not spathulate), brown or pale brown. Hymenium: White; not inspers. Interascal Hyphae: Distinctly branched, not or scarcely anastomosed. Subhymenium: White. Hypothecium: White; not inspers.

Asci: Cylindrical.

Ascospores: Physcia-type, c. 8 per ascus, ellipsoid, (19.5)-22-27.5-(32) µm long, (8.5)-10-13-(16) µm wide; septa present; transversally septate; 1-transversally septate; wall thickened at the septum, becoming pigmented, dark brown, middle brown, or pale brown.

Conidiomata: Present; sparse or moderately abundant.

Conidia: Bacilliform (-subcylindrical); (4)-5-(6) µm long; 1 µm wide.

Secondary Metabolites: Present; only in the upper part of the cortex, atranorin (and zeorin, ocassionally leucotylin and/or other triterpenes).

Spot Tests: Present reactions. Upper surface: K + deep yellow, C –, KC –, PD + yellow; cortex: KC + deep yellow, – medulla: K – C –, KC –, PD – soredia: K – KC –.

(report generated 13.Nov.2007)