Coenogonium barbatum Lücking, Aptroot & Umaña

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 : 107-108

Coenogonium barbatum Lücking, Aptroot & Umaña , Fungal Diversity 23: 273 (2006). ( Fig. 5J )

Thallus filamentous, projecting horizontally from the margin of leaves, caespitose, beard-shaped, composed of several tufts of filaments connected at the base, with a single point of attachment, yellowish green, up to 10 mm long and broad, ecorticate; prothallus absent. Photobiont Trentepohlia , cells cylindrical, in distinct filaments, 50–60 × 25–30 μm diam. Apothecia produced on the underside of the thallus, substipitate, rounded, 0.3–0.5 mm diam. and 100–130 μm high; disc soon convex, pale yellow to yellow-orange; margin thin, not prominent, smooth, cream-colored. Excipulum paraplectenchymatous with radiating cell rows, 25–55 μm broad, colorless, I+ sordid yellow-green; cells isodiametric and thin-walled, 4–7 μm diam. Hypothecium 10–20 μm high, colorless. Hymenium 60–80 μm high, colorless, I+ permanently blue. Ascospores uniseriate, 1-septate, ellipsoid, 7–9 × 2–2.5 μm, 3–3.5 times as long as broad. Pycnidia not observed. Chemistry: no substances detected by TLC.

Distribution and habitat:—Foliicolous on the margin of leaves in understory of hill evergreen forests at 830 m. Until recently this species was only known from the type locality, a lowland rainforest in Costa Rica, but it probably has a pantropical distribution. Presumably, it has been mistaken for a young specimen of C. linkii and neglected because it is often infertile. Coenogonium barbatum is a new addition to the Thai lichen biota.

Remarks:—While our collection is morphologically identical with the type (compare Rivas Plata et al., 2006, Fig. 3 C ), some anatomical details differ as well as the iodine reaction of the hymenium, e. g. the diameter of the Trentepohlia filaments is greater (15–20 μm in the type) and some of the spore details are missing in the original description. However, the dimensions given here are the same as in the type (Lücking, pers. comm.). This recently described species is similar to C. linkii and C. leprieurii , but clearly differs in having an Usnea -like thallus rather than a shelf-like and semi-circular thallus which is present in the latter.

Material from Thailand examined:— Nakhon Ratchasima: Khao Yai National Park, Pakchong district ; hill evergreen forests along main road no. 2077 at km 2, on leaves of Cocculus laurifolius , 830 m, 14°23’46.61’’ N, 101°22’45.63’’ E, 24 April 2000, K. Papong RU-19082-1 ( RAMK 004687 ) .

Figures

FIGURE 3. Mangrove forest in Trat Province.

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.