Arthonia lopingensis A. Zahlbr. (1930: 36)

Frisch, Andreas, Grube, Martin, Kashiwadani, Hiroyuki & Ohmura, Yoshihito, 2018, Arthoniaceae with reddish, K + purple ascomata in Japan, Phytotaxa 356 (1), pp. 19-33 : 21-23

Arthonia lopingensis A. Zahlbr. (1930: 36) .

Type.— China, Yünnan. “Prope vicum Tjintjischan ditionis oppida Loping, in silva frondosa Collins”, corticolous on Schoepfia jasminodora, Handel-Mazzetti 1976 (Herbarium Zahlbruckner 10107; WU holotype). Fig. 3A , 4A .

THALLUS parasitic on Graphis spp. or independent with age, pale fawn to pale olivish brown, matt, coherent, up to 0.4 mm tall, largely endophloeodal; prothallus line not observed; photobiont trentepohlioid, the cells rounded to elliptical, 4–13 × 2–10 μm, in short chains or single cells; mycobiont hyphae 1.5–2.5 μm wide, scattered throughout the host thallus and bark; calcium oxalate crystals not observed. ASCOMATA lirellate, the lirellae ± with unequal dichotomic branching, 0.5 × 0.1–0.2 mm, typically aggregated in irregular star-shaped clusters about 0.5–1.0 mm diam., immersed in the (host) thallus to weakly emergent; disc flat, brown to brownish-black, epruinose or with a weak yellow to orange pruina; margins slightly elevated, with dense yellow to orange pruina; proper exciple yellow to orange, 10–25 μm wide, of compacted and parallel paraphysoidal hyphae; epithecium yellow to orange, 5–10 μm tall, conglutinated; hymenium hyaline to pale orange-brown, 50–70 μm tall, conglutinated, the asci distantly spaced; hypothecium hyaline to pale orange-brown, 10–25 μm tall, conglutinated, of compact, short-celled prosoplectenchymatic hyphae (cells 3–8 × 1–2 μm); quinoid pigments mainly as ca 1 μm wide granules in proper exciple and epithecium and, in addition, to a lesser degree also as amorphous pigmentation in hymenium and hypothecium; paraphysoids branched and netted, 1.5–2.0 μm wide, loosely arranged, somewhat wavy; paraphysoid tips unpigmented, slightly widened to 1.5–2.5 μm, loosely intertwined, often extending horizontally above the asci. ASCI of the Arthonia-type, clavate, with broadly triangular ocular chamber, 32–40 × 13–17 μm (n=10), lateral walls ca 1 μm thick, base not abruptly deflected, 8-spored (spores in 2–3 irregular rows). ASCOSPORES narrow ovoid to slipper shaped with enlarged apical cell, (11.0–)11.4–13.6(–15.0) × (3.5–)4.0–5.2(–5.5) μm (n=30; l: mean=12.5, STD=1.14; w: mean=4.6, STD=0.55), (2–)3-septate, hyaline, turning brown with fine granular ornamentation in the perispore at late maturity. PYCNIDIA not observed.

Chemistry.— Parietin (major) and ± psoromic acid (minor to trace), ± norstictic acid (from host thallus, major) in solvents B′ and C detected by TLC (12/Jp4, 12/Jp5, and Asahina 106 tested). Thallus hyphae ( Arthonia ) I+ pale blue, KI+ blue; ascomatal gels I dil + blue, I+ deep blue, KI+ deep blue; asci with KI+ blue ring structure in the tholus; ascospore walls and septa I–, KI–. The pigments dissolve in K with purple solution in which purple granules precipitate.

Ecology and distribution.— Arthonia lopingensis in Japan grows mainly as a juvenile parasite on the thallus of Graphis spp. , including G. handelii Zahlbruckner (1930: 44) , G. intricata Fée (1825: 42) and G. mikuraensis Ohmura & Nakanishi in Ohmura et al. (2016: 5), in coastal forests along the pacific coast of central Honshu and the Izu and Ogasawara Islands. The species was collected from broad-leaf deciduous and evergreen trees including Acer buergeriana , Machilus thunbergii and Morus australis . The species is further known from the type locality in China.

Notes.— Most available specimens of A. lopingensis grow as small parasitic thalli on Graphis spp. ( Fig. 3A ), including the type from China, but specimens forming larger autonomous thalli are known, e.g., Asahina 106 (TNS). Arthonia lopingensis belongs to a small group of Arthonia species containing parietin in the ascomata, including among others Arthonia borbonica Ertz, Elix & Grube (2010: 222) from Réunion and the European Arthonia elegans (Ach.) Almquist (1880: 19) . Arthonia lopingensis closely resembles A. elegans with respect to its general morphology and by parietin and psoromic acid as specialized metabolites. However, the ascospores of A. lopingensis are smaller (11–15 × 3.5–5.5 μm vs 14–18 × 4–7 μm), the hymenium is lower (50–70 μm vs 60–90 μm) and the ascomata are more slender on average. Parasitic stages similar to that of A. lopingensis could not be observed in the investigated specimens of Arthonia elegans , although the species often grows intermixed with Graphis scripta (L.) Acharius (1809: 145) in its natural habitat and specimens where G. scripta gets overgrown at the margins by the Arthonia are not rare.

Aptroot & Sparrius (2003) reported A. elegans from Taiwan, but their identification most likely refers to A. elegans as understood in The lichens of Great Britain and Ireland ( Coppins & Aptroot 2009) and may refer to Coniocarpon fallax (Ach.) Grube in Frisch et al. (2014: 737). We have not seen that specimen. New to Japan.

Specimens examined.— Japan, Honshu. Prov. Izu (Pref. Shizuoka): Mt Nesugata, Shimoda-city (34°40′N, 138°57′E), on bark of Machilus thunbergii , elev. 170 m. 08. ii. 2012, A. Frisch 12/Jp4, 12/Jp5 (TNS, hb Frisch); Prov. Kii (Pref. Wakayama): Tanabe, Nishi-Muro-gun. 10. iv. 1925, Y. Asahina 106 (TNS); ibid., Tanabe, without precise locality, on Acer buergeriana . 20. xii. 1911, Imai 633 (TNS). Izu Islands (Tôkyô Metropolis): along the route between Sato and Ienosawa, Mikura-Jima Island, on Graphis mikuraensis (holotype) on bark of tree branch, elev. 500 m. 15. vii. 1981, Higuchi 10474 (TNS). Ogasawara Islands (Tôkyô Metropolis): Haha-jima, Sekimon (26°41′03.5″N, 142°09′36.6″E), on twig of Morus australis , elev. 250 m. 22. iii. 2013, Y. Ohmura 9795 (TNS).

Exsiccate specimens of Coniocarpon elegans (Ach.) Duby (1830: 675) (syn. C. ochraceum (Duf.) Fries 1830: 380 ) examined.— Hepp, Flechten Europas 354: Zürich, an der Rinde junger Buchen. Hepp [cited after Hepp, P. (1858)] (TNS, UPS); Rabenhorst, Lichenes europaei 337: [ Italy, Piemont], ad corticem Tiliae microphyllae in sylva le riane supra Trobaso in valle Intrasca ad Verbanum. 1857, de Notaris (TNS); Vrang, Lichenes exsicc. ex herb. rel. W. v. Zwackh: Schweiz, Zürich. Hegetschweiler (TRH); ibid., Baden, Heidelberg, Königsstuhl. 1857, Zwackh (TRH).

Figures

FIGURE 3. Thallus and ascomata. A. Arthonia lopingensis on Graphis handelii (Frisch 12/Jp5, TNS). B. Coniocarpon cinnabarinum (Frisch 13/Jp128, TNS). C, D. Arthonia sanguinaria (Frisch 13/Jp59, TNS): A margin of thallus, B ascomata. E. Arthonia picea (Kashiwadani 14142, TNS). F. Arthonia eos (Thor 26000, GZU). Scale bars:A, B=0.5 mm, C, E, F=1 mm, D=1.5 mm.

FIGURE 4. Details of the ascomata. A. Arthonia lopingensis, Arthonia-type ascus and spores (Ohmura 9795, TNS). B. Arthonia sanguinaria, young spores and crystal needles formed in LCB (Ohmura 6609, holotype, TNS). C, D. Arthonia picea (Kashiwadani 14742, TNS), C Arthothelium-type ascus with young spores, D spores. Scale bars = 10 μm.