Placopsis (Nyl.) Linds.

Lichens Pan-Z (2007) - Flora of New Zealand Lichens - Revised Second Edition Pan-Z

PLACOPSIS (Nyl.) Linds., 1866

Type: Placopsis gelida (L.) Linds. [=Lichen gelidus L.]

Description : Flora (1985: 399).

Key

With soredia or isidia

Without soredia or isidia

Thallus isidiate

Thallus sorediate

Isidia small, globular, easily eroded and leaving pits

Isidia large, finger-like, rarely eroding

clavifera

Thallus small, 1–3(–5) cm diam.; lobes separating at apices; upper surface not glossy

cribellans

Thallus larger, 2–5(–8) cm diam.; lobes contiguous, separated by long, narrow cracks; upper surface glossy like polished ivory

subcribellans

Thallus not rusty-orange; soralia olive, green or whitish

Thallus rusty-orange; soralia grey-blue

lateritioides

Soralia well-delimited, not becoming confluent

Soralia confluent, often spreading over whole thallus surface

argillacea

Thallus rosette-forming, not of small squamules; soralia often with a well-defined margin

Thallus of small squamules (sometimes coalescing)

Soralia with dark-green to blackish soredia; 5- O -methylhiascic acid present

lambii

Soralia with pale-greenish or greyish soredia; 5- O -methylhiascic acid absent

gelida

Marginal squamules with spots of white pruina; soralia vesicular-excavate to spreading

microphylla

Marginal squamules without spots of white pruina; soralia capitate

rhodocarpa

Cephalodia elongated, jointed or vein-like

Cephalodia sessile, rounded, rosette-forming, not elongated, jointed, or vein-like

Yellow anthraquinones (K+ red-purple) present in lower medulla; apothecial discs pale pinkish- or brownish-pruinose; ascospores 20–28.5 × 15–17.5 μm

murrayi

Yellow anthraquinones absent from lower medulla; apothecial discs epruinose; ascospores 17–25.5 × 10–15 μm

venosa

Thallus on sandy soil, silt or clay

Thallus on rock

Thallus effuse–indeterminate or of congested papillae

Thallus, thick, spreading, not effuse–indeterminate or of congested papillae

Thallus effuse–indeterminate

subparellina

Thallus areolate, of congested papillae

hertelii

Apothecial discs bright candy-pink, with a thin to thick, white pruina

rhodophthalma

Apothecial discs dark brown-black, epruinose

trachyderma

Thallus not rust-coloured, orange or reddish

Thallus rust-coloured, orange to reddish

bicolor

Apothecia immersed (aspicilioid) at maturity

Apothecia sessile at maturity

Thallus wholly or partly pruinose

Thallus epruinose

macrophthalma

Thallus pale to dark olive-green to brownish grey when moist; margins neatly pleated; with distinctive parallel cracks separating lobes; patches of glistening, granular pruina at or near margins, sometimes spreading to entire surface; apothecia developed centrally, 0.5–1.5 mm diam.; thalline margin concolorous with thallus; hymenium 250–300 μm tall; ascospores occupying upper half of ascus, 20–25 × 10–12–5 μm

aspicilioides

Thallus pale greyish brown to pinkish brown; margins microphylline or squamulose, without parallel cracks; minutely velvety pruinose; apothecia scattered in small groups, 0.1–0.5 mm diam.; thalline margin whitish; hymenium 175–200 μm tall; ascospores occpying whole of ascus, 20–27.5 × 10–17.5 μm

durietziorum

Thallus wholly or partly pruinose

Thallus epruinose

Thallus ±continuous, not eroding in bands centrally and forming concentric rings

Thallus eroding in bands centrally and forming partial or complete concentric rings on substratum

centrifuga

Marginal prothallus absent

Marginal prothallus present, brown, fibrous to varnish-like; thallus squamulose or areolate with scattered spots of white, glistening pruina or entire surface thickly white-pruinose; apothecia prominent, discs brown-black, epruinose; thalline margin white-pruinose; scospores 21–32 × 8–10 μm

pruinosa

Thallus pruina in scattered spots or patches

Thallus ±uniformly grey-white, velvety pruinose

fuscidula

Thallus without laminal pseudocyphellae; cephalodia not white-pruinose

Thallus with distinctive, flattened marginal lobes, often white-pruinose at apices, and with scattered, punctate to effigurate white pseudocyphellae; cephalodia often white-pruinose; apothecial discs red-brown to brown-black, roughened-papillate, epruinose; ascospores 30–40 × 8.5–13.5 μm

elixii

Apothecial discs red-brown, slightly pruinose; hymenium 280–320 μm tall; ascospores 25–30 × 12–21 μm

subgelida

Apothecial discs vivid candy-pink, with a thick white pruina, cracking when dry and appearing gyalectiform; ascospores 20–28.5 × 10–13 μm

rhodophthalma

Marginal prothallus prominent, black or brownish

Marginal prothallus absent

Thallus areolate or congested papillate; prothallus flat, closely attached

Thallus distinctly lobate with characteristic flattened apices; prothallus arachnoid, often ascending at apices and lobe margins

perrugosa (exposed, riverine form)

Prothallus brownish, varnish-like, 3–6 mm wide; thallus minutely areolate, of congested papillae; apothecia 0.5–1 mm diam., solitary or in small groups; the discs pale to dark carmine-red, epruinose; thalline margin persistent, concolorous with thallus or whitish; hymenium 160–180 μm tall; ascospores 25–33.5 × 5–6 μm

hertelii

Prothallus black, visible as a marginal rim, 0.5–1 mm wide; thallus of flat, interlocking, jigsaw-like areolae; apothecia 1–2 mm diam., in concentric lines, the discs brown to black, epruinose; thalline margin occluded; hymenium 80–140 μm tall; ascospores 12–18 × 6–8.5

illita

Asci 8-spored; ascospores 12–25 μm long

Asci 4-spored; ascospores (37–)40–57.5(–64) × 20–30 μm

macrospora

Upper surface deeply areolate or verrucose-papillate, especially centrally

Upper surface plane, not areolate or verrucose-papillate

Upper surface verrucose-papillate or wrinkled–knobbly centrally

Upper surface areolate centrally, not verrucose-papillate

Upper surface brown-grey, olive-brown or brown-black (Neofuscelia -like), wrinkled–verrucose, verrucose-papillate or contorted-verrucose centrally; lobe apices distinctively flattened (snakeskin-like); ascospores 15–21.5 μm long

perrugosa

Upper surface pinkish brown to dark red-brown, wrinkled–knobbly centrally; lobe apices swollen, never flattened; ascospores 20–23 μm long

brevilobata

Thallus K− (salazinic acid absent)

Thallus K+ blood-red (salazinic acid present)

salazina

Surface of areolae not minutely cerebriform (×10 lens)

Surface of areolae minutely cerebriform; areolae separated by deep cracks 0.2–1 mm wide, and appearing as distinctive "islands"

dusenii

Upper surface without maculae; lobes convex–bullate, 0.5–3 mm wide, in parallel lines; apothecia scattered, solitary or 2–3-together; thalline exciple thick, swollen, often obscuring disc

gelidioides

Upper surface conspicuously white-maculate when moist; lobes narrow, 0.2–0.5 mm wide, convex; apothecia densely clustered, small, in radiating rows and often occupying most of thallus centre; thalline margin thin, sometimes excluded

polycarpa

Cephalodia sessile

Cephalodia immersed; apothecia small; thalline exciple verrucose; ascospores ovoid, 20–25 (–27) × 10–12.5(–15) μm

tararuana

Apothecia not swollen-ampliate or pertusarioid

Apothecia swollen-ampliate, appearing pertusarioid; ascospores 20–22 × 11–12 μm

ampliata

Thallus surface smooth, matt; cephalodia 1–5 mm diam., central or in concentric circles; apothecial disc pale to dark red-brown, sometimes white-pruinose; ascospores (14–)16–22(–24) × (7.5–)9–12(–13.5) μm

stenophylla

Thallus surface punctate-depressed, glossy (like polished ivory); cephalodia solitary, central, 5–20 mm diam.; apothecial disc dark-brown to brown-black,roughened to radially fissured, epruinose; ascospores 15–18 × 6–8 μm

dennanensis

Placopsis is characterised by a lobate, crustose thallus, sessile to subimmersed, laminal cephalodia, and lecanorine apothecia. Species occur in highly oceanic, temperate habitats with c. 40 named species known worldwide, the majority from the Southern Hemisphere (Lamb 1947, 1963; Awasthi & Agarwal 1968; Hawksworth 1972a; Follmann et al. 1991; Lumbsch et al. 1993; Brodo 1995a; Moberg & Carlin 1996, 1999; Lumbsch 1997b; Galloway 2001a, 2001b, 2001c, 2002d, 2004a, 2004b, 2005, 2006; Henssen 2003) though current investigations on the genus underway in the temperate Southern Hemisphere indicate a substantial increase on this number (unpublished observations). Formerly recognised in the order Lecanorales and the family Trapeliaceae (Hertel 1970a; Eriksson & Hawksworth 1998), Placopsis is now included in the family Agyriaceae (Lumbsch 1997b; Döring & Lumbsch 1998; Eriksson et al. 2004; Pennycook & Galloway 2004) in the order Agryriales (Lumbsch et al. 2001b) together with the genera Agyrium Fr., Amylora Rambold, Anzina Scheid., Lithographa Nyl., Orceolina Hertel (Poulsen et al. 2001), Placynthiella Elenkin, Ptychographa Nyl., Rimularia Nyl., Trapelia M.Choisy, Trapeliopsis Hertel & Gotth. Schneid., Xylographa (Fr.) Fr.

Recent molecular work on 11 species of Placopsis and related genera in the Agyriales shows that Placopsis as currently circumscribed is paraphyletic, with species of Orceolina nesting within the genus (Schmitt et al. 2003). These authors also suggest resurrecting Aspiciliopsis macrophthalma as an independent, monospecific genus.

Species of Placopsis colonise siliceous rock and lava on smooth ice-worn faces, outcrops, boulders or scree slopes, sand, gravel or cinders in glacial, periglacial, riverine and coastal environments, and rarely on decorticated wood impregnated with silt. It is common on disturbed surfaces and associates with species of the following lichen genera: Caloplaca, Gyalidea, Lecidella, Porpidia, Stereocaulon, Usnea sect. Neuropogon, Verrucaria and Zahlbrucknerella, and with the terrestrial alga Trentepohlia. The genus is particularly well-represented in the Southern Hemisphere, the major areas of speciation being New Zealand, with at least 40 species present in high-rainfall areas (Galloway 2001a, 2001b, unpublished observations), and southern South America where 18 species are currently recognised (Zahlbruckner 1928 – as Lecanora sect. Placopsis; Lamb 1947; Follmann et al. 1991; Galloway 2002d), with further new species awaiting description. Detailed investigation of the New Zealand Placopsis mycobiota over the past few years has uncovered a three-fold increase in numbers of species present there, and undoubtedly the number of species occurring in cool temperate southern South America is also considerably higher than what is presently recognised. High-rainfall, recently deglaciated areas are especially rich in species of Placopsis where these lichens add considerable amounts of fixed nitrogen to the soil nitrogen budget (Galloway 1992a, 1998d, 2002c). Placopsis is highly speciose in New Zealand, and to the 13 species recorded in the Flora (Galloway 1985a), an additional ten species were recently added to the New Zealand mycobiota (Galloway 2001a, 2001d, 2002d, 2004a, 2004b). The taxon P. parellina (Nyl.) I.M.Lamb, formerly recorded from New Zealand as a very polymorphic species (Lamb 1947; Galloway 1985a), is now regarded as a Chilean endemic (Galloway 2002d: 92–93), with the earlier subspecific forms ampliata, argillacea and microphylla now treated as independent species (q.v.). This account discusses 36 species. A detailed monograph of the New Zealand species is in preparation and will be published elsewhere.

Placopsis (Nyl.) Linds.

Key

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