The genus Fuscopannaria (Pannariaceae) is characterized by small squamules, often with a black prothallus, a hemiamyloid hymenium, simple ascospores with a smooth epispore, and a tube structure in the ascus tip. Most species are cyanobacterial, but two green-algal species are known; Fuscopannaria viridescens M. Jørg & Zhurb. and F. granulifera M. Jørg. & Upreti. Fuscopannaria viridescens grows terricolously in arctic and alpine habitats in Alaska and Russia (Jørgensen & Zhurbenko Reference Jørgensen and Zhurbenko2002), whereas F. granulifera is known only from the type locality in India where it grows epiphytically near the tree line in the Himalaya (Jørgensen Reference Jørgensen2004). Vahliella globuligera (Fryday & M. Jørg.) M. Jørg., formerly in Fuscopannaria, is another squamulose, green-algal arctic species, distinguished from F. viridescens by its granular thallus and amyloid sheets instead of a tube/plug at the ascus apex.
Fuscopannaria viridescens has a distinctive habit, with plane, distal lobes that become upright and imbricate centrally (Fig. 1A), aptly likened to “cats-paws” (Jørgensen & Zhurbenko Reference Jørgensen and Zhurbenko2002), which is similar to the habit of well-developed Baeomyces placophyllus Ach. It is also the only green Fuscopannaria in North America, making it hard to mistake for other species, except possibly an overzealous Psoroma. The genus Psoroma has a dirty blackish blue hymenial amyloid reaction and ascospores with a textured epispore. Collections of F. viridescens made recently in the Denali and Gates of the Arctic National Parks and Preserves (Alaska, USA), possess minute, imbricate, darkened lobes (when wet) (Fig. 1E), which, upon further inspection, turned out to be cephalodia. We further studied this material to assess whether it could still be accommodated in F. viridescens s. lat., despite having cephalodia.
Fuscopannaria viridescens. A, habit, wet, showing green colour and apothecia (T. Wheeler 4721); B, cross-section of, and arrow pointing to, centre of cephalodium (T. Wheeler 4721); C, cross-section of thallus and arrows pointing to cephalodium (T. Wheeler 4721); D, habit, dry, fully exposed brown form (T. Wheeler 4215); E, close-up showing cephalodia (arrows) (T. Wheeler 4721); F, ascus stain showing tube structure (T. Wheeler 4721); G, ascopores with smooth epispore (T. Wheeler 4721). Scales: A, D & E=1 mm; B=25 µm; C=100 µm; F=10 µm.
All specimens were studied using standard light microscopy. Ascomatal, ascospore and thallus measurements were made on material mounted in distilled water. Hymenial amyloid reactions were observed by staining apothecia cross-sections with a 2% solution of iodine potassium iodide (IKI). Ascus tip structures were viewed by pretreating cross-sections with potassium hydroxide (K), flushing with distilled water and staining with IKI. Standard cortex and medullary spot test reactions were observed using a 10% aqueous solution of potassium hydroxide (K), para-phenylenediamine dissolved in ethanol (PD), sodium hypochlorite (C) and K followed by C (KC) administered to the thallus with a small pipette.
All our fertile specimens possessed simple ascospores, 20–26×7–10 µm, with a smooth epispore (Fig. 1G), a distinct dark blue ascal plug with an indistinct pale central tube, similar in appearance to a poorly developed Porpidia-type ascus (Micarea-type ascus tip of Spribille & Muggia Reference Spribille and Muggia2013) (Fig. 1F), and a hemiamyloid reaction in the hymenium. The upper cortex was sometimes composed of a thin, clear, prosoplectenchymatous layer over a more frequent thick, clear paraplectenchymatous lower layer. The cephalodia contained Nostoc sp. embedded in a fungal matrix that formed furrows of the cyanobiont (Fig. 1B & C), giving the cephalodia a streaky appearance when viewed from above. All spot tests were negative.
The characteristics we observed in all our Alaskan material matched the descriptions of F. viridescens except for the presence of cephalodia and, to a lesser degree, the upper cortex structure and ascospore size. Jørgensen & Zhurbenko (Reference Jørgensen and Zhurbenko2002) reported the upper cortex of F. viridescens to be sclerenchymatous (syn. prosoplectenchyma). This periclinially arranged hyphal layer was not as consistent in our material as the thick paraplectenchymatous layer below it, which Jørgensen & Zhurbenko (Reference Jørgensen and Zhurbenko2002) did not report. We observed only the thick paraplectenchymatous cortex in the isotype, indicating the periclinially arranged hyphae mentioned by Jørgensen & Zhurbenko (Reference Jørgensen and Zhurbenko2002) perhaps varies with environmental conditions or is more frequent in certain parts of the thallus. The isotype had ascospores 12·5–20·0×7·5–10·0 µm in size, consistent with the species description. However, the range of ascospore length observed in our material was six microns longer (Jørgensen & Zhurbenko Reference Jørgensen and Zhurbenko2002). We believe our ascospore measurements to be within the range of variation for the species because collections of F. viridescens are often infertile specimens and the variation in ascospore dimensions is probably under-recorded. We also confirmed that the isotype had the same laminal cephalodia with Nostoc as the other specimens we examined. The cephalodia were most likely overlooked when this species was described because they are often similar in colour to the rest of the thallus, appearing as tiny, laminal, imbricate lobes (Fig. 1E). In the extreme environment where F. viridescens occurs, thallus colour can vary from pale green (Fig. 1A) to very dark brown (Fig. 1D), depending on exposure and hydration. We conclude that all of the tripartite Fuscopannaria material we examined is attributable to F. viridescens. To the best of our knowledge, this is the first case of a Fuscopannaria possessing cephalodia.
Our finding of cephalodia on one of only two green-algal species of Fuscopannaria is significant but not surprising. Many genera with cyanobacteria as their primary photobiont also have tripartite species (e.g. Peltigera, Pseudocyphellaria, Nephroma). Similarly, many tripartite species occur in Pannaria, Psoroma and Degeliella, primarily in the Southern Hemisphere, in the otherwise cyanobacterial Pannariaceae. In North America, the only tripartite species of the Pannariaceae other than Fuscopannaria viridescens are species of Psoroma. However, we were unable to find any species in the Pannariaceae worldwide with only a green-algal photobiont, other than F. granulifera. This leads us to suspect that F. granulifera, like F. viridescens, probably has cephalodia that were overlooked, or it belongs to a different family where green-algal species occur. Pending examination of F. granulifera, our finding implies that the entire Pannariaceae always has either a primary or secondary cyanobacterial photobiont.
Specimens examined. USA: Alaska: Denali National Park & Preserve, Primrose Ridge, 63°45′12·92″N, 149°23′08·53″W, alt. 1430 m, J. Walton 6069 (ALA); Gates of the Arctic National Park & Preserve, Summit Lake, 68°04′51·68″N, 150°28′29·07″W, alt. 1230 m, T. Wheeler 4215 (hb. Wheeler); Kurupa Lake, 68°20′46·56″N, 154°30′29·72″W, alt. 1330 m, P. R. Nelson 12-1181 (OSC); Narvak Lake, 66°53′58·02″N, 155°34′17·28″W, alt. 1025 m, P. R. Nelson 12-523 (OSC); Upper Nigu River, 67°57′03·99″N, 155°23′ 26·68″W, alt. 850 m, T. Wheeler 4721 (hb. Wheeler); North Slope Borough, Barrow, 79°19′N, 156°36′ 10″W, alt. 1 m, A. Fryday 8234 (MSC); Kobuk Valley National Park, Kobuk River, alt. c. 30 m, M. Zhurbenko 00352 (BG—isotype!).
