Arthonia picea Vain. (1921: 301)

Frisch, Andreas, Grube, Martin, Kashiwadani, Hiroyuki & Ohmura, Yoshihito, 2018, Arthoniaceae with reddish, K + purple ascomata in Japan, Phytotaxa 356 (1), pp. 19-33 : 23-25

Arthonia picea Vain. (1921: 301) .

Type.— Philippines, Luzon. Sorsogon: Irosin, ad corticem arboris, Elmer 14923 pr.p. (TUR-VAIN 28591! lectotype, here selected; B!, US! isolectotypes) .

= Arthonia fuscococcinea Willey ined. in herb. US.

= Arthonia spec. in Willey (1890: 23).

FIG. 3E , 4D

THALLUS pale olivish grey to pale buff (almost whitish), thin, matt, smooth, coherent, in section up to 0.1 mm tall, partly endophloeodal; prothallus line black, thin, in contact to other lichens; photobiont trentepohlioid, the cells rounded to elliptical, 7–10 × 3–6 μm, in short chains or single cells, dense; mycobiont hyphae 1.5–2.5 μm wide, hyaline, weakly conglutinated; calcium oxalate crystals not observed. ASCOMATA dispersed, maculate, immersed to moderately emergent, elliptical to shortly lirelliform to lobed, dark brownish red, 0.5–1.8 × 0.4–0.7 mm, margin not differentiated; disc flat to weakly convex, ± level with the thallus, epruinose; proper exciple not differentiated, the margins of the ascomata without asci and with more closely netted paraphysoids; epithecium orange-red, 15–20 μm tall; hymenium orange-red, 80–100 μm tall, the asci closely spaced; hypothecium orange-red, 10–35 μm tall, conglutinated, of short-celled, densely branched and netted prosoplectenchymatic hyphae (cells 3–7 × 0.7–1.0 μm); quinoid pigments in numerous ca 1 μm wide granular crystals and as amorphous pigmentation in the gelatinous matrix of epithecium, hymenium and hypothecium; paraphysoids densely branched and netted, 1.5–2.0 μm wide, somewhat wavy, often forming more compacted strands of anticlinal hyphae between the asci; paraphysoid tips only slightly widened to 1.5– 2.5 μm, without pigmentation of the walls. ASCI of the Arthothelium-type, broadly clavate, with broad triangular ocular chamber, 60–70 × 18–20 μm (n=5), lateral walls 1.0–1.5 μm thick, base not abruptly deflected, 8-spored (spores in 3–4 irregular rows). ASCOSPORES narrow elliptical with capitate upper cell, (26.0–)27.0–32.4(–35.0) × (9.0–)9.7–11.5(–12.0) μm (n=40; l: mean=29.7, STDV=2.65; w: mean=10.6, STDV=0.87), 4–6-septate, hyaline first, later brown, slightly constricted at the septa, with granular ornamentation in the perispore at late maturity. PYCNIDIA not observed.

Chemistry.— Pigments A6 (major), A5 (major) and A4 (minor to trace) in solvents B′ and C detected by TLC. Thallus hyphae I+ pale red, KI+ pale blue; ascomatal gels I dil –, I+ deep red, KI+ blue; asci with KI+ blue ring structure in the tholus (at the inner side of the wall left and right of the ocular chamber and extending down along the inner ascus wall); ascospore walls and septa I–, KI–. The pigments dissolve in K with purple solution without crystal formation.

Ecology and distribution.— Arthonia picea was collected on the Ogasawara Islands from the trunk of an unidentified broad-leaf tree in dense forest and from exposed branches of Ficus boninsimae .

Notes.— This species superficially resembles a small A. sanguinaria (see below) but differs in the larger ascospores with granular ornamentation in the perispore when mature (26–35 × 9–12 μm vs 15–21 × 5–8 μm), the broadly clavate asci of the Arthothelium-type, the different reaction of the hymenial gels to iodine (I+ deep red vs I+ blue), and a different pattern of pigments (A4–6 vs A7). Confluentic and psoromic acids are absent. The phylogenetic analysis shows that the two species are not closely related ( Fig. 2 ). Arthonia picea is widely distributed in tropical regions. For the Pacific region we are aware of collections from Australia, New Caledonia Philippines (type) and U.S. A (Hawaii). The isotype of A. picea in B has ascospores up to 7-septate, but otherwise agrees well with our recent collections from the Ogasawara Islands. New to Japan.

Specimen examined: — Japan, Ogasawara Islands (Tôkyô Metropolis): Chichi-jima , Minami-Fukurozawa. 22. vi. 1977, H. Kashiwadani 14142 (TNS) ; ibid., Haha-jima, Mt Chibusa (26°39′05″N, 142°10′08″E), on exposed Ficus boninsimae trees, elev. 388 m. 23. iii. 2013, A. Frisch 13/ Jp 107, 124 & Y. Ohmura, H. Kashiwadani (TNS) .

Figures

FIGURE 2. Best tree obtained from RAxML analysis showing the phylogenetic position of A. picea, A. sanguinaria and the Japanese specimens of Coniocarpon cinnabarinum (in bold and indicated by black bold supporting branches) in Arthoniaceae.Additional branches leading to taxa containing K+ reddish pigments are indicated in bold grey. Support values of the RAxML analysis (first) and Bayesian analysis (second) are indicated.

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.