Coenogonium luteum (Dicks.) Kalb & Lücking, In

Kalb, Jutarat, Boonpragob, Kansri & Kalb, Klaus, 2016, New Coenogonium species (Ostropales: Coenogoniaceae) from Thailand, new reports and a revised key to the species occurring in the country, Phytotaxa 283 (2), pp. 101-122 : 115

Coenogonium luteum (Dicks.) Kalb & Lücking, In : Lücking & Kalb, Bot. Jahrb. Syst. 122 (1): 32 (2000). ( Fig. 7F )

Lichen luteus Dicks., Fasc. Plant. Crypt. Brit. 1: 11 (1785); Dimerella lutea (Dicks.) Trevis., Rend. Reale Ist. Lomb. Sci. , ser. 2, 13 (3): 66 (1880).

Thallus crustose, usually corticolous or muscicolous, rarely foliicolous, continuous, thin, smooth, grey, dull or partly shiny, up to 70 mm diam., with a distinct hyaline, paraplectenchymatic corticiform layer in part, 7–10 μm thick; prothallus absent. Photobiont Trentepohlia , cells angular to rounded, mostly in irregular plates, partly short threads, cells 5–13 × 5–12 μm. Apothecia epiphyllous, sessile, rounded in outline, 0.5–2.0 mm diam., 200–300 μm high; disc plane, concave in younger apothecia, orange-yellow to orange; margin distinct, slightly prominent, cream-colored to whitish. Excipulum paraplectenchymatous with irregularly arranged cells, 50–100 μm broad, outer part I+ yellow-brown, inner part I–; cells globose to elongate, thin- or partly thick-walled, 3–8 × 3–7 μm. Hypothecium 20–30 μm high, colorless to pale yellowish. Hymenium 60–75 μm high, colorless, I+ blue then quickly greyish brown, then reddish brown. Asci 55–70 × 6–8 μm. Ascospores oblique-uniseriate or irregularly uniseriate, broadly ellipsoid, 1- septate, 7–12 × 2.5–3.5 μm, 2.4–3.6 times as long as broad. Pycnidia wart-shaped, immersed in thallus or erumpent, 0.05–0.15 mm diam., cream colored or very pale yellowish. Conidia broadly ellipsoid-bacillar, non-septate 3–5 × 2–3 μm. Chemistry: no substances detected by TLC.

Distribution and habitat:—Cosmopolitan. Originally described from Great Britain, it occurs in oceanic or suboceanic climates in Europe and North America, but also in the tropical and subtropical regions of North, Central and South America, Africa and Asia. It usually grows on bark and over mosses, rarely on leaves. In Thailand, it seems to be a ± rare species on bark of trees and muscicolous on granite in secondary forests and dry evergreen forests from 680– 830 m.

Remarks:— C. luteum in the strict sense is distinguished by its rather large apothecia with an orange disc and broadly ellipsoid, uniseriate ascospores. C. luteolum (Kalb) Kalb & Lücking and C. lueckingii Y. Joshi, Gagarina, Halda & Hur are very similar. The former differs mainly by having smaller ascospores (7–9 × 3 μm) and conidia (2.5–3.5 × 1–2 μm). The latter differs in having smaller apothecia (0.4–0.9 mm diam.), irregularly biseriate ascospores and a distinct white prothallus. Also similar is C. strigosum Rivas Plata, Lücking & Chaves, but this species differs in having a green and shiny thallus with a white prothallus.

Material from Thailand examined:— Nakhon Ratchasima Province: Khao Yai National Park, dry evergreen forests along trail from Pha Kuai Mai (camping area) to Heo Su Wat waterfall, 680 m, 14°26’07’’ N, 101°24’50’’ E, 14 March 2008, K. Kalb (herb. K. Kalb 37034) ; ibid., secondary forests, ca. 200 m behind Nhong Khing , 830 m, 14°25’7.29’’N, 101°22’18.52’’ E, 15 January 1999, K. Papong RU-16432-2 ( RAMK 004683 ) .

Figures

FIGURE 7. Habitus photographs of Coenogonium species.A. Coenogonium interplexum (RAMK 027802), showing a young substipitate apothecium (upper part), scale 0.4 mm. B. Coenogonium isidiatum (KK 24025), scale 2 cm. C. Coenogonium isidiiferum (KK 41459), marginal part of thallus, scale 0.4 mm. D. Coenogonium isidiiferum (KK 41459), exfoliating thallodiscs, leaving ± round holes in the thallus, scale 0.2 mm. E. Coenogonium leprieurii (RAMK 27804), scale 1 mm, scale of inlet 0.5 mm. F. Coenogonium luteum (KK 24052), scale 1 mm.