Thallus corticolous, endophloeodal to epiphloeodal, loosely corticated or ecorticate, thin to c. 120 µm, whitish gray to gray, greenish gray, usually dull to slightly glossy, smooth to uneven, continuous to cracked. Algal layer well developed, continuous or discontinuous, densely integrated with crystals. Calcium oxalate crystals abundant, small to large, mostly aggregated to dispersed. Medulla indistinct to endophloeodal. Vegetative propagules not seen.

Ascomata conspicuous, up to c. 0.7 (~0.9) mm diam., mostly rounded, apothecioid, erumpent, solitary to completely fused. Disc grayish to blackish or flesh colored, whitish pruinose, becoming partly visible, 0.11~0.26 mm diam. Pores variable, small to moderate to c. 0.25~0.42 mm diam., rounded to irregular, proper exciple apically to completely visible from above, usually free only in the upper parts, off-white, often somewhat shrunken, entire, incurved to straight. Thalline margin rounded, entire, incurved to straight, concolorous with the thallus, 0.02~0.09 mm thick. Proper exciple free, mostly hyaline to slightly pale or brownish, sometimes covered with grayish to dark grey granules on tips, 15~25 µm thick, I-. Lateral paraphyses conspicuous, to c. 18 µm long. Epihymenium, hyaline to dark brown or grayish due to inspersion of crystals, 10~17 µm high. Hymenium hyaline, clear, moderately conglutinated, 50~100 µm high. Paraphyses parallel or slightly interwoven, unbranched, tips slightly thickened, c. 1~1.5 µm thick. Subhymenium hyaline, indistinct. Asci clavate, 8-spored, 60~95 × 12~18 µm, I-. Ascospores hyaline, transversely septate, fusiform, with rounded to sub-acute ends, occasionally pale yellowish when old or decayed, 50~77 × 6~12 µm, with 17~24 locules. Locules lenticular; ascospore wall and endospore thick; wall often with a thin to thick halo. I+ blue to faint blue.

Thallus K-, C-, PD- (- indicates no color reaction); no secondary compounds detected upon thin layer chromatography.

The species is most common to tropical and subtropical regions of Africa, Australia and Asia [², ³]. In South Korea it is reported from evergreen forests of Mt. Halla in Jeju Island at an altitude between 600~900 m.

This species closely resembles Thelotrema subtile and T. pseudosubtile Mangold in having trans-septate, hyaline ascospores and a thallus lacking secondary metabolites. However, the latter species differ in having ascospores of smaller range (25~60 × 6~10 µm). Further, T. pseudosubtile has a less noticeable free proper exciple. Another similar species, Thelotrema nureliyum Hale, has a thick, verrucose thallus with comparatively large ascomata (> 1 mm) and ascospores of 60~220 × 10~20 µm.

Jeju Island, Mt. Halla, Gwanum Temple Trail, 33°25'04.08" N, 126°32'52.01" E, alt. 619 m, on tree bark, 1 Jun 2012, Hur et al., KoLRI 120957, KoLRI 120962. Seongpanak Trail, 33°22'76.3" N, 126°36'80.1" E, alt. 834 m, on tree bark, 6 Jul 2012, Hur et al., KoLRI 121515.

Thallus corticolous, endophloeodal to epiphloeodal, irregularly corticate to c. 150 µm thick, whitish gray to greenish gray to gray green, dull to slightly glossy, usually smooth, continuous. Algal layer usually well developed, continuous or discontinuous, densely integrated with crystals. Calcium oxalate crystals abundant, small to large, clustered. Medulla indistinct to endophloeodal. Vegetative propagules not seen.

Ascomata conspicuous to c. 0.31~0.56 mm diam., somewhat rounded, apothecioid, immersed to scarcely erumpent, solitary. Disc grayish to blackish, whitish pruinose, becoming partly visible, up to 0.15 mm diam. Pores variable, small to c. 0.11~0.25 mm diam., rounded to irregular. Proper exciple apically to completely visible from above, usually free only in the upper parts, off-white, often somewhat shrunken, usually entire to slightly split, incurved. Thalline margin appears rounded, entire, incurved, concolorous with the thallus, 0.09~0.15 mm thick. Proper exciple almost free, mostly hyaline to slightly pale at apices, sometimes covered with grayish to dark gray granules on tips, 16~36 µm thick, I- to rarely amyloid at base corners. Lateral paraphyses often inconspicuous to conspicuous apically to c. 16 µm long. Epihymenium grayish, crystalline, 12~14 µm high. Hymenium hyaline, clear, moderately conglutinated, 160~200 µm high. Paraphyses parallel or slightly interwoven, unbranched, tips slightly thickened, c. 1~1.5 µm thick. Subhymenium hyaline, indistinct to c. 15 µm high. Asci clavate, 1~4-spored, 150~170 × 25~30 µm, I-. Ascospores hyaline, muriform, cylindrical to oblong-ellipsoidal or broadly fusiform, occasionally pale yellowish when old or decayed, 75~125 × 14~26 µm, with numerous locules. Locules rounded to angular, subglobular. Ascospore wall and endospore thin. Thin to thick gelatinous sheath sometimes present, I+ faint blue.

Thallus K-, C-, PD-; no secondary compounds detected upon thin layer chromatography.

The species is most common among the palaeotropical regions of Asia [¹⁷]. In South Korea it was collected at an altitude between 800~900 m from evergreen forests of Mt. Halla of Jeju Island.

Thelotrema lepademersum resembles T. lepadinum and T. monosporum Nyl. with respect to the size of ascospores (up to 120 × 60 µm) and number of ascospores (1~4) per ascus, but other characteristics differ slightly. Specifically, T. lepadinum has thick walled, persistently hyaline ascospores, and comparatively larger apothecia, whereas T. monosporum lacks cortical structures, has indistinctly lepadinoid apothecia and non-amyloid ascospores that soon become brown. The halonate ascospores and almost colorless exciple of the examined specimen show close proximity to T. rugatulum Nyl., but the smooth thallus, mostly immersed and smaller apothecia and ascospore size lead the material to be provisionally placed in Thelotrema lepademersum. Accordingly, collection of additional specimens and their characterization is required to confirm the position of the specimen.

Jeju Island, Mt. Halla, Seongpanak Trail, 33°22'76.3" N, 126°36'80.1" E, alt. 834 m, on tree bark, 6 Jul 2012, Hur et al., KoLRI 121517.

Thallus corticolous, epiphloeodal to endophloeodal, corticate, thin, up to c. 135 µm, gray green to pale grayish green, dull to slightly glossy, usually smooth, continuous. Algal layer well developed, continuous or discontinuous due to integration of crystals. Calcium oxalate crystals abundant, small to large, clustered; medulla indistinct, endophloeodal. Vegetative propagules not seen.

Ascomata conspicuous, up to c. 1.5 mm diam., somewhat rounded, apothecioid, erumpent, solitary, appears hemispherical. Disc not visible from above, rarely becoming partly visible, grayish, pruinose. Pores variable, small to moderately large, to c. 0.19~0.58 mm diam., almost rounded, proper exciple apically to rarely completely visible from above, more or less free, off-white, often somewhat shrunken, usually entirely to slightly split, incurved. Thalline margin rounded, entire, thin to thick, incurved, concolorous with the thallus, 0.24~0.42 mm. Proper exciple apically to completely free, thin to thick, hyaline to pale brown, mostly higher than hymenium, forming a roof like structure, 30~35 (~68) µm, I-. Lateral paraphyses conspicuous, c. 25 µm, reaching 57 µm above hymenium. Epihymenium, dark, crystalline, 12~13 µm high. Hymenium hyaline, clear to c. 180 µm high, moderately conglutinated. Paraphyses parallel or slightly interwoven, unbranched, tips slightly thickened, 1~1.5 µm thick. Asci clavate, 1~4-spored, 140~145 × 20~25 µm, I-. Ascospores hyaline, muriform, oblong~ellipsoidal or broadly fusiform, with sub-acute ends, occasionally pale yellowish when old or decayed, 40~90 × 10~20 µm, with numerous locules. Locules rounded to angular, subglobular to irregular. Ascospore wall and endospore thick, halo not seen, I- or I+ (+ indicates color reaction) faintly bluish.

Thallus K-, C-, PD-; no secondary compounds detected upon thin layer chromatography.

The taxon is subcosmopolitan and widely distributed in temperate to subtropical regions in both hemispheres and in the tropical mountains [², ³]. In South Korea it is collected from rather exposed trees of evergreen forests in Mt. Halla of Jeju Island at an altitude of 600~700 m.

Thelotrema lepadinum shows morphological resemblance to several species of Thelotremas. str., but most closely resembles T. crassisporum Mangold, T. subtile and T. adjectum Nyl. T. crassisporum contains stictic acid as the thallus compound and has small ascospores, whereas T. adjectum has a layered exiple, flesh colored apothecial disc and 4~8-spored asci. T. subtile has smaller ascomata and trans-septate ascospores.

Jeju Island, Mt. Halla, Gwanum Temple Trail, 33°25'28.5" N, 126°33'68.7" E, alt. c. 619 m, on tree bark, 7 Jul 2012, Hur et al., KoLRI 121536.

Thallus corticolous, epiphloeodal, loosely corticate, thin, up to c. 100 µm, gray green to whitish gray or greenish gray, dull, speckled with crystals, continuous. Algal layer well developed, continuous or discontinuous due to integration of crystals. Calcium oxalate crystals abundant, small to large, clustered; medulla indistinct to endophloeodal. Vegetative propagules not seen.

Ascomata conspicuous to c. 0.4~0.6 mm diam., somewhat rounded, apothecioid, erumpent, mostly solitary to rarely fused, appears hemispherical. Disc partly to completely visible, flesh colored, pruinose, 0.1~0.19 mm. Pores variable, small to c. 0.15~0.32 mm diam., rounded, proper exciple apically to completely visible from above, free, off-white, often somewhat shrunken, incurved. Thalline margin rounded to irregular, entire, thin to thick, incurved, concolorous with the thallus, 0.12~0.19 mm. Proper exciple, apically to completely free, thin to thick, hyaline to pale brown or marginally brown, 30~95 µm, I-. Lateral paraphyses conspicuous, c. 25 µm. Epihymenium, hyaline, crystalline, 12~15 µm high. Hymenium hyaline, clear to c. 185~250 µm high, moderately conglutinated. Paraphyses parallel or slightly interwoven, unbranched, tips slightly thickened, 2~2.5 µm thick. Asci clavate, 1-spored, 185~190 × 35~40 µm, I-. Ascospores hyaline, muriform, oblong-ellipsoidal or broadly fusiform, with rounded to sub-acute ends, 94~150 × 14~30 µm, with numerous locules. Locules rounded to angular, ascospore wall and endospore thick, halo not seen, I+ bluish or I+ faintly bluish.

Thallus K-, C-, PD-; no secondary compounds detected upon thin layer chromatography.

The species is distributed in the eastern palaeotropics and has been reported in Japan [¹⁸]. In South Korea it was collected from tree barks in evergreen forest of Mt. Halla of Jeju Island at an altitude around 1,000 m.

Thelotrema similans exhibits similarity to T. lepadinum in having a loosely corticated thallus, pruinose apothecial disc, muriform, hyaline ascospores and lack of secondary metabolites. However, 1~4-spored asci, thick walled small ascospores and an almost hyaline proper exciple of Thelotrema lepadinum clearly separate it from T. similans. The observed specimen can be confused with Thelotrema capense Zahlbr., but the latter species has non-amyloid ascospores and is restricted to Africa [²].

Jeju Island, Mt. Halla, Seongpanak Trail, 33°22'38.8" N, 126°34'16.4" E, alt. 1,181 m, on tree bark, 8 Aug 2012, Hur et al., KoLRI 121657.