Arthrorhaphis citrinella (Ach.) Poelt

Frisch, Andreas, Ohmura, Yoshihito, Holien, Håkon & Bendiksby, Mika, 2022, A phylogenetic survey of the ascomycete genus Arthrorhaphis (Arthrorhaphidaceae, Lecanoromycetes) including new species in Arthrorhaphis citrinella sensu lato, TAXON 71 (5), pp. 936-962 : 952-953

Arthrorhaphis citrinella (Ach.) Poelt ≡ Lichen citrinellus

Ach. in Kongl. Vetensk. Acad. Nya Handl. 1795: 135.

1795 – Lectotype (designated by Obermayer in Nova

Hedwigia 58: 301. 1994): Suecia (H-ACH No. 262 A

[barcode H9501180]!).

MycoBank 344680

See Fig. 7B,C for images of the species.

Description. – Thallus lichenised, forming small irregular colonies over saxicolous bryophytes, up to 2.5 cm in diam., often dispersed and poorly delimited, (greenish) yellow, usually entirely formed of loose, rarely compacted coralloid aggregations of coarse granular soredia, 0.05–0.15(–0.2) mm; medulla absent; Ca-oxalate crystals absent. Apothecia laterally or centrally attached to the granular thallus, more rarely separated, single or clustered to 2–8, 0.4–1.0 mm, adnate to shortly and broadly stipitate, black, matt, the thick margin first protruding, later level with the flat to distinctly convex, more or less coarsely rugose disc. Epihymenium dirty to brownish olive green, HNO 3 green, 15–25 μm. Hymenium unpigmented to pale olivish green, densely inspersed, 90–140 μm. Subhymenium 50–90 μm, dirty to brownish olive green. Exciple 55–80 μm wide, dark dirty to brownish olive green, darker towards the outer edge. Paraphyses sparsely branched and anastomosed, 1–1.5 μm wide. Asci 100–130 × 10–13 μm. Ascospores acicular, parallel in the asci, (45.0–)58.0–88.0 (–102.0) × (2.0–)2.5–3.5(–4.0) μm (n = 63; l: mean = 73.1, SD = 14.72; w: mean = 2.9, SD = 0.51), (6–)7–11(–15)-septate. Pycnidia absent.

Chemistry. – Rhizocarpic acid (major), epanorin (minor).

Distribution and ecology. – Arthrorhaphis citrinella is common and widespread in Scandinavia. It has been further confirmed for Austria (on morphology), Iceland, and Scotland, and might be more widely distributed in the Northern Hemisphere. The elevation ranges from sea-level to 1800 m. Arthrorhaphis citrinella typically overgrows acrocarpous mosses ( Andreaea , Bryum , Grimmia , Schistidium , Tortula , etc.) on exposed to shaded steep rock walls and boulders, on acidic to more basic rock types. The species has often been found associated with Lepraria spp. , Racodium rupestre , and filamentous cyanobacteria ( Scytonema ). Parasitic juvenile stages on other lichens have not been observed.

Notes. – In its current narrow circumscription, Arthrorhaphis citrinella is characterised by rather small, poorly delimited thalli formed of loose to compacted aggregations of coarsely granular soredia, and by the absence of parasitic stages on Baeomyces spp. (rarely on other lichens). Discrete areolae, which in strongly sorediate specimens of A. vulgaris are usually at least indicated, and a well-delimited medulla are lacking. All specimens in this study for which ecological information was available were collected from steep rock walls and siliceous boulders, overgrowing saxicolous bryophytes rather than soil. For a distinction from A. farinosa , see under that species.

Selected specimens examined (a total of 36 specimens seen). – AUSTRIA. Steiermark, Schladminger Tauern, Gasselhöhehütte zum Mittersee, 47°21 ′ 25 ″ N, 13°35°45 ″ E, 26 Aug 2001, Obermayer 9090 ( GZU) . FINLAND. Uusimaa, Varttila, Kivelänkallio, Grid 27°E 6707 330, 1 Sep 1991, Pykälä 8793 (H) ; Etelä-Karjala, Parikkala, Melkoniemi S, Leunanmäki, Grid 27°E 6825 624, 7 Aug 1986, Vitikainen 11794 (H) . Etelä-Savo, Sulkava, Sairalanmäki, Grid 27°E 68471 5637, 5 Aug 1986, Vitikainen 11657 (H) . GREAT BRITAIN. Scotland, VC 90, Angus, Glen Clova, Ben Reid, Jun 1954, Duncan s.n. (E00721892); ibid., VC 105, West Ross, Beinn Fhada, Allt a Choire Chaoil, Grid: NH 0033 2127, 28 Jul 2010, Harrold PH10346 (E00468586). ICELAND. Austurland, S-Múlasýsla, Stöðvarfjörður, Hvalsnes, 64°49 ′ N, 13°53 ′ W, 10 Jul 1997, Svane 97 SS 9745 D (C) . NORWAY. Telemark, Vinje, E of Båtstodi , UTMWGS84: 32V MM 2289 2223, 1 Apr 2010, Timdal 11259 (O-L-161820) . Rogaland, Rennesøy, Helland, UTMWGS84: 32V LL 096 562, 28 Mar 2011, Johnsen s.n. (BG-L-92402) . Hordaland, Granvin, E of Havås , UTMWGS84: 32V LN 72 13, 5 Oct 1994, Ihlen 465 (BG-L-32814) . Sogn og Fjordane, Aurland, Flåm, UTMWGS84: 32V LN 979 486, 8 Sep 1993, TØnsberg 19156 (BG-L-24848) . Nord-Trøndelag, Steinkjer, Mokk farm, 63°58 ′ 19.50 ″ N, 12°07 ′ 36.96 ″ E, 4 Aug 2015, Frisch 15/No100 (TRH-L-652426) . SWEDEN. Bohuslän, Lysekil, Skaftö, Islandsberg, 29 Aug 1992, Hafellner 30507 ( GZU) . Dalarna, Särna parish, Fulufjället N.P., Skärhamrarna, 61°37 ′ 14.04 ″ N, 12°47 ′ 37.20 ″ E, 3 Jul 2016, Thor 33549 ( UPS) . Södermanland, Österhaninge parish, Tyresta National Park , Lycksjön, UTMWGS84: RN 6564333 1638101, 11 Jan 2009, Thor 23013 (UPS-L-192446) .

Figures

Fig. 7. A, Arthrorhaphis catolechioides (Moberg & Owe-Larsson NZ2:5, UPS); B, A. citrinella (Odelvik 10598, S); C, A. citrinella (Frisch 15/No100, TRH); D, A. farinosa (Ohmura 9312, TNS); E, A. farinosa (Thor 33718, UPS); F, A. bullata (Ohmura 10730, TNS). — Scale: A, B, E & F, 1 mm; C, 0.5 mm; D, 5 mm. Photos: A. Frisch.