Degelia cyanoloma (Schaer.) H. H. Blom & L. Lindblom, comb. et stat. nov

Pannaria plumbea var. cyanoloma Schaer., Enum. Criticae Lich. Eur.: 36 (1850); type: [France, Normandie], in sylva Briquebec, Delise, undated (G — lectotype, selected by Jørgensen Reference Jørgensen1978: “Briquebec, Delise”).

Note: For a discussion of the epithet cyanoloma and the specimens collected by Delise, see Jørgensen (Reference Jørgensen1978).

(Fig. 1A, B & E)

Fig. 1. Degelia species, morphology. A, B & E, D. cyanoloma; A, habitus (Lindblom & Blom L421), thalli of Normandina pulchella (Borrer) Nyl. are often observed growing on D. cyanoloma, as shown here; B, lobe tip (Lindblom & Blom L420); E, apothecia (Lindblom & Blom L421). C & F, D. atlantica; C, lobe tip (2005, Knutsen); F, apothecia (2008, Blom); D & G, D. plumbea; D, lobe tip (Tønsberg 3876); G, apothecia (2000, Krumsvik). All material in BG Scales: A = 2 mm; B – G = 1 mm.

Thallus foliose, forming rosettes, mostly c. 5 –15 (–25) cm diam., composed of concave, successive segments each ending in a transverse curved ridge-like structure (resembling a lobe margin), fine radiating striae present towards thallus margin, squamules absent, lobes (1·1–)3·0(–5·0) mm wide, thallus margin blue-black, ascending, thick, smooth, glossy; upper surface light to pale grey or pale bluish-grey. Thallus heteromerous, c. 200–250 μm thick, with a (24–)32(–44) μm thick paraplectenchymatous upper cortex of anticlinal hyphae; photobiont layer close to the upper cortex, (32–)48(–88) μm; medulla colourless, of densely conglutinate, periclinal hyphae, (48–)92(–108) μm; hypothallus prominent, greyish to blackish, not or slightly extending beyond the thallus margins.

Apothecia common, sparse to abundant, but sometimes lacking, often aggregated; disc dark red-brown to blackish, occasionally bright red, (0·6–)1·1(–2·0) mm diam., margin smooth, blackish. Hymenium colourless, 120 – 160 μm tall; paraphyses simple, tips up to c. 5 μm wide, slightly swollen. Asci clavate-cylindrical, 8-spored. Ascospores simple, ellipsoid, colourless, with or without oil droplets, (15–)16·7(–20) × c. 6–8 μm.

Conidiomata pycnidia, present in about one third of thalli studied, laminal, immersed, wart-like, ostiole pale. Conidia bacilliform, c. 3–6 × 1 μm.

Ecology and distribution. Degelia cyanoloma grows on bark, but frequently also on rock. Populus tremula L. is by far the most important phorophyte in western Norway but the species is also recorded growing on Corylus avellana L., Fraxinus excelsior L. and occasionally on Alnus glutinosa (L.) Gaertn. Typical habitats are oak-aspen forests or aspen stands on humid E- and N-facing slopes close to the sea and in coastal coves. Usually it grows together with species of the Lobarion community (see Rose Reference Rose1988), and among them Degelia atlantica, Lobaria pulmonaria (L.) Hoffm., L. virens (With.) J. R. Laundon and Pannaria rubiginosa (Ach.) Bory are the most frequent companion species in our study area.

Degelia cyanoloma is a large lichen, and in all the sites studied where it grows together with D. atlantica and D. plumbea, it is distinctly larger than these species. Judging from situations on aspen trees, where numerous, both juvenile and large adult thalli of the three species could be studied together, we conclude that growth in D. cyanoloma is faster than in the two other species.

In western Norway D. cyanoloma is known from coastal areas and westernmost fjord districts from Rogaland county north to Sogn og Fjordane county, mostly in areas with a January mean temp above 0°C. Thus its Norwegian distribution is quite similar to that of D. atlantica (Krog et al Reference Krog, Østhagen and Tønsberg1994: fig. 32). Outside Norway we have studied specimens from Great Britain (Scotland), Ireland, France (Normandy), Portugal and Spain (see list of specimens studied), and D. cyanoloma seems to belong to the group of euoceanic species (Jørgensen Reference Jørgensen1996).

Notes. The combination of large size, pale greyish thallus (not or very slightly bluish when dry) composed of successive concave, trough-shaped segments, and the dark apothecia is indicative of D. cyanoloma in the field. The species is usually found with apothecia, lacks isidia, and is clearly most likely to be confused with D. plumbea as it has been in the past. The thallus is thicker and more robust than that of D. plumbea, and the lobes are wider. The thallus surface of D. cyanoloma appears quite smooth (Fig. 1A & E) compared with the rough thallus surface of D. plumbea owing to the presence of squamules (Fig. 1G) and coarse radiating ridges, often with thick knob-like squamules in the latter species. In D. cyanoloma the thallus surface is distinctly, but finely striate (Fig. 1A & E), whereas an irregular network of narrow whitish maculae is characteristic of the thallus surface in D. plumbea, particularly towards the lobe margins (Fig. 1D). A further useful field character is found in the thallus lobes: in D. cyanoloma, the lobe margin is thick and swollen, distinctly glossy, and quite smooth (Fig. 1B) whereas in D. plumbea, the lobe tips are thinner, quite dull, and the margin is mostly irregular owing to presence of narrow incisions or finger-like lobules (Fig. 1D). The apothecial discs of both D. cyanoloma and D. plumbea are reddish when wet. However, in dry material, the very dark red-brown or blackish discs of D. cyanoloma is a good character distinguishing it from D. plumbea in Norwegian populations.

Clearly, previous descriptions of D. plumbea include characteristics also of D. cyanoloma in our sense. The scallop-like appearance, partly a result of the presence of transverse, crescent-shaped ridges, was included in the descriptions of both D. atlantica and D. plumbea by Jørgensen (Reference Jørgensen1978). However, this character is more pronounced in D. cyanoloma (Fig. 1A & E) than in D. atlantica, but absent or indistinct in D. plumbea. The segments between the transverse ridges are distinctly concave (trough-shaped) in D. cyanoloma but flatter in D. atlantica and, particularly, in D. plumbea. These characteristics give D. cyanoloma a strong resemblance to species of the genus Coccocarpia (see Arvidsson Reference Arvidsson1982). The most important morphological characters separating Degelia atlantica, D. cyanoloma and D. plumbea in Norway are summarized in Table 1.

Table 1. Morphological characters that can be used for separating Degelia atlantica, D. cyanoloma and D. plumbea.

* Measurements are given as (min. value obs.–) arithmetic mean obs. (–max. value obs.).

In qualitative anatomical characters D. cyanoloma is very similar to D. plumbea and D. atlantica, but differs from both species in the thicker thallus. Degelia cyanoloma has been included in D. plumbea, the type species of Degelia sect. Amphiloma, and obviously belongs here (cf. Jørgensen & James Reference Jørgensen and James1990). However, it shares more morphological character states with D. atlantica than with D. plumbea. The overall structure of the thallus surface including the lack of squamules and the thick even lobe margins, distinguish both D. cyanoloma and D. atlantica from D. plumbea. Further, both species lack the pale brownish, yellowish-brown or dull olivaceous secondary colours of the thallus surface that are characteristic of D. plumbea. On the other hand, such thallus colours are found in the rare species D. ligulata. Moreover, D. ligulata possesses a network of whitish maculae on the thallus surface similar to that found in D. plumbea, and the diagnostic schizidia resemble the coarse knob-shaped squamules seen in many specimens of D. plumbea. Accordingly, based on morphology, we hypothesize that D. cyanoloma is more closely related to D. atlantica than to D. plumbea, whereas D. plumbea and D. ligulata are closely related.

Herbarium specimens labelled D. plumbea from Macaronesia (in BG and FR) are not readily referred to either D. cyanoloma or D. plumbea. They need further study, preferably including molecular methods, and may represent an additional taxon. We have studied only a single specimen labelled D. plumbea from North America (Canada, Newfoundland, 2007 Mac Pitcher; BG) and it clearly belongs to that species.

Selected specimens examined (all in BG). Norway: Rogaland: Finnøy, Talgje, 2001, Johnsen s. n.; Vindafjord, Stråtveit, 1997, Gaarder 2308; Strand, Ramnås, 2000, Krumsvik s. n. (with D. plumbea). Hordaland: Austevoll, Klumra, 2007, Blom s. n.; Bømlo, Spissøya, 2005, Knutsen s. n.; Andal, 2005, Knutsen s. n.; Tysnes, Smievoll, Pollen, 2007, Lindblom & Blom L407; Tysnes, Beltestadknappen, 2008, Lindblom & Blom L421; Os, Storomsvågen, 2008, Lindblom & Blom L420. Sogn og Fjordane: Flora, Gruvla, 1991, Gaarder 373; Hyllestad, Lekva, 1992, Gaarder 685. —Great Britain: Scotland: V.C. 98, Argyll: Seil, Ballachuan, 1980, Botnen Sk113; V.C. 97, Westerness: Glen Nevis, 1925, Lid s. n.—Ireland: V.C. H16, West Galway: Kylemore Abbey, 1982, Schindler s. n.—Portugal: Algarve, N of Monchique, 1980, Jones s. n. —Spain: Caaveiro, 1986, coll. ignot.