Flora of New Zealand Series

Type : Leioderma pycnophorum Nyl.

Description : Thallus foliose in orbicular, ±loosely attached rosettes, 10–15 cm diam. Lobes flat or subconvex to concave with involute margins, discrete to imbricate, often ±incised with margins slightly thickened at apices, ±crenate. Upper surface smooth, scabrid or arachnoid–tomentose, usually grey-blue, rarely brownish. Lower surface pale, white at margins, often buff or ochre-brown centrally with clustered fascicles of white to blue-black rhizohyphae. Photobiont cyanobacterial, Scytonema, in small chains. Ascomata apothecia, usually abundant except in sorediate species, small, laminal, sessile, often crowded, to 2.0 mm diam.; disc plane to concave, epruinose, pale to dark red-brown with distinct, pale, proper exciple; thalline exciple lacking; cyanobiont layer penetrating apothecia along subhymenium; hymenium I+ persistently blue (one species is I−). Asci with distinct amyloid cap, but no internal amyloid structures. Ascospores ellipsoidal, with smooth walls. Conidiomata pycnidia, common, mainly marginal, ±papillate, black, shining, to 0.2 mm diam., conidia Sticta -type. Chemistry −, or occasional and spasmodic development of ursolic acid.

Leioderma is a predominantly Southern Hemisphere genus in the Pannariaceae (Eriksson et al. 2004; Pennycook & Galloway 2004; Eriksson 2005), most closely related to Erioderma, but distinguished from it by an absence of chemical characters and small, laminal apothecia (Jørgensen 2003c). Seven species are currently known (Jørgensen 2003c, 2004e; Jørgensen & Arvidsson 2004), with New Zealand (4 species), Australia and Ecuador (3 species) being the main present-day areas of speciation. It is absent from Africa, Europe and Asia (apart from the the Pacific seaboard), and from E of the Rockies and Andes in North and South America respectively, with the exception of L. glabrum in Brazil. It is thus a Gondwanaland genus with two major biogeographical elements: (1) a warm temperate–subtropical or Tethyan element comprising Leioderma erythrocarpum and its sorediate counterpart L. sorediatum, and also L. duplicatum and L. glabrum and (2) a cool temperate or austral element comprising L. pycnophorum, the generitype. Species of Leioderma are primarily corticolous, being epiphytes of forest trees and shrubs. It is discussed in detail in Galloway & Jørgensen (1987) and in Jørgensen & Galloway (1992b: 257–260). The genus Fuscoderma (q.v.) was formerly included as a distinct subgenus of Leioderma (Galloway & Jørgensen 1987; Jørgensen & Galloway 1989, 1992b).