Coenogonium convexum J. Kalb & K. Kalb, 2016

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 : 108-109

Coenogonium convexum J. Kalb & K. Kalb , sp. nov. ( Figs. 5A , 6A )

Mycobank MB 818608

Similar to Coenogonium nepalense (G. Thor & Vězda) Lücking, Aptroot & Sipman , but differs in having distinctly smaller apothecia (0.5–0.8 mm in C. nepalense ) with convex discs even in young apothecia (discs concave when young in C. nepalense ) and a light olive-green and shiny thallus (grey to greenish grey and usually dull in C. nepalense ).

Etymology:—The specific epithet refers to the convex apothecia.

Type:— THAILAND. Chiang Mai province: Doi Suthep-Pui National Park ENE of Chiang Mai, trail to Monthathan waterfall, epiphyllous in a humid Dipterocarpus forests. 18°49’00’’ N, 98°55’28’’ E, 700 m ; 17 March 2008, K. Kalb (41133), K. Buaruang, S. Jariangprasert & W. Saipunkaew ( RAMK, holotype) .

Thallus crustose, foliicolous or corticolous, continuous, thin, 50–70 μm high, smooth, light olive-green, shiny, 10–30 mm diam., with 3–5 μm thick corticiform layer; no distinct prothallus present. Photobiont Trentepohlia , cells angular to rounded, in irregular plates or short threads, cells cylindrical, 10–15 × 6–8 μm. Apothecia sessile, rounded, 0.25– 0.45 mm diam. and 180–220 μm high; disc initially plane, but soon distinctly convex, pale yellow-orange; margin thin, not prominent, soon reflexed and no longer visible from above, rough, of same color as the disc. Excipulum paraplectenchymatous with radiating cell rows, 50–70 μm broad, colorless, outer part I+ yellow-brown, inner part I–; cells isodiametric to elongate, thin-walled, 5–7 × 3–5 μm. Hypothecium 20–30 μm high, colorless to pale cream-colored. Hymenium 75–90 μm high, colorless, I+ blue then quickly sordid green then dark brown. Asci 55–65 × 3–6 μm. Ascospores mostly monoseriate, a few irregularly biseriate, narrowly ellipsoid, 1-septate, 10–13 × 2.5–3 μm, 3.3–5.8 times as long as broad. Pycnidia not observed. Chemistry: no substances detected by TLC.

Distribution and habitat:—Currently known from Thailand and Australia. Foliicolous in the understory of a humid Dipterocarp forests (holotype) at 700 m, and corticolous in a coastal, tropical rainforest in Queensland, Australia at 5 m elevation.

Remarks:—The new species belongs in a difficult species complex centered around C. nepalense and C. usambarense (Vězda & Farkas) Lücking & Kalb. Coenogonium convexum has smaller apothecia which soon become convex at a very early stage of development, while they are 0.4–0.8 mm diam. in C. nepalense with a concave disc when young. C. usambarense and C. convexum have apothecia of similar size, but those of C. usambarense differ in being brown-orange in color and in having an erumpent margin and a concave disc. In addition, C. usambarense has a dull thallus. Despite of the different habitats, the specimens from Thailand and Australia are identical in all respects.

Additional material examined:— AUSTRALIA. Queensland: A few km N of Cardwell; Edmund Kennedy NP, corticolous in a coastal tropical rainforest with Avicennia marina , Bruguiera gymnorhiza, Lumnitzera ramosa, Rhizophora mucronata, Xylocarpus granatum, Terminalia seriocarpa, Livistona drudii etc., 5 m; 18°12’48’’ S, 146°00’44’’ E; 23 August 2002, K. Kalb 40796 (WIS).

Figures

FIGURE 5. A. Coenogonium convexum (KK 41133), transverse section through the crustose thallus showing the corticiform layer, scale 15 μm. B. Thallodiscs laying upside down on the thallus of Coenogonium isidiiferum (KK 41459), scale 0.3 mm, scale of inlet 0.1 mm. C. Coenogonium luteum (Schumm 8577), exciple coloured with lactophenol-anilinblue, scale 20 μm. D. Coenogonium leprieurii (RAMK 027804 b), ascus tip stained permanently blue with Lugol‘s solution. E. and F. Coenogonium aff. borinquense (KK 38577) showing different arrangement of ascospores within the asci of the same section, scales 5 μm and 10 μm. G. Coenogonium subborinquense (KK 38820), irregular shaped pycnidia, scale 0.2 mm. H. Coenogonium subluteum (RAMK 004684 b), hymenium stained with Lugol‘s solution; after some time, the upper part still remains blue while the lower part has turned red brown. I. Coenogonium luteum (Schumm 8577), hymenium stained with Lugol‘s solution; after some time, the whole hymenium has turned red brown. J. Conogonium barbatum (RAMK 004687), habitus, filamentous thallus projecting from the margin of a leaf, scale 1.5 mm.

FIGURE 6. Habitus photographs of Coenogonium species. A. Coenogonium convexum (KK 41133), scale 1 mm. B. Coenogonium coronatum (KK 41136), scale 0.5 mm, scale of inlet 0.15 mm. C. Coenogonium dilucidum (KJ 41439), scale 0.25 mm. D. Coenogonium epiphyllum (RAMK 009100), scale 0.25 mm. E. Coenogonium frederici (Isotype, KK 41445), scale 0.5 mm. F. Coenogonium geralense (KK 41446), scale 1 mm.