Thelotrema subtile and Verrucaria muralis New to Korea

Abstract

The paper describes two new records of micro-lichens from South Korea. Detailed taxonomic descriptions and comments are presented for both of the studied taxa. The lichen genus Thelotrema is reported for the first time in Korea.

The present paper is a continuation of a study of micro-lichens from Korea (Joshi et al., 2009a, 2009b). During a recent field trip to Gitdae-bong and Mt. Sorak, Gangwon Province, the authors found two micro-lichens growing on bark and rock. After consulting various literatures, the species were identified as Thelotrema subtile Tuck. and Verrucaria muralis Ach.

This paper contributes to our current knowledge of micro-lichens reported in this country for the first time, and expands our knowledge of micro-lichen diversity in Korea. Detailed taxonomic descriptions, along with chemistry, ecology, and illustrations are provided for both species.

Specimens were evaluated using standard microscopic techniques and were hand-sectioned under a NIKON CPS 1068908 dissecting microscope. All measurements were made on materials mounted in water, and lactophenol cotton blue (LCB) was used only as a stain. For characteristics including the size of the thallus, ascoma, and the thickness of the hymenium, subhymenium, hypothecium, exciple, involucrellum, and ascospore, 10 measurements per specimen were recorded. The dimensions of the ascospores are generally expressed in terms of smallest mean recorded largest mean recorded. Spot test reactions were conducted on hand sections of thalli and apothecia under an OLYMPUS BX 50 microscope. Secondary metabolites were identified via TLC as described by Elix et al. (1987) and White and James (1985). The terminology used for tissues is generally consistent with that of Nash III and Gries (2002). Voucher specimens of all collections have been deposited in the herbarium of the Lichen and Allied Bioresource Center, Korean Lichen Research Institute (KoLRI), Sunchon National University with their duplicates in the Korea National Herbarium (KH), Korea.

Taxonomic Treatment of the Species

Thelotrema subtile Tuck. (Fig. 1A, B)

Fig. 1.

Habit and Apothecial anatomy of two lichen species newly reported in this study. A (Bar = 5 µm) and B (Bar = 50 µm) Thelotrema subtile Tuck; C (Bar = 5 µm) and D (Bar = 100 µm) Verrucaria muralis Ach.

Amer. J. Arts Sci., ser. 2, 25: 426 (1858).

Diagnostic characteristics

Thallus corticolous, epiphloedal, whitish, dull to slightly glossy, smooth, continuous to slightly fissured, thin, prothallus not seen (but when present thin and black). Protocortex discontinuous, occasionally becoming conglutinated and forming a true cortex of periclinal hyphae. Algal layer poorly to well developed, 15~22 µm thick, continuous or discontinuous, calcium oxalate crystals abundant, scattered or clustered. Medulla endophloedal. Vegetative propagules absent.

Ascomata apothecia, dispersed, conspicuous, up to 0.5 mm diam., ± rounded to somewhat irregular, sessile, solitary to marginally or rarely completely fused, ± distinctly emergent, hemispherical to urceolate or subglobose. Disc usually becoming partially visible from above in older ascomata, grey, ± distinctly whitish-pruinose. Pores small to gaping, to c. 0.4 mm diam., ± rounded to irregular, entire to slightly split, the proper exciple apically to more often completely visible from above, apically pale, brownish towards the base, occasionally shrunken, incurved to somewhat erect. Thalline rim margin thin to thick, usually becoming wide to gaping, entire to split, rarely somewhat eroded, ± rounded to irregularly rounded, mostly incurved and concolorous with thallus. Proper exciple free, thick, hyaline to largely pale yellowish internally, yellowish to greyish brown marginally, apically often dark brown, rarely amyloid at the base. Hymenium to c. 150 µm thick, not inspersed, distinctly conglutinated; paraphyses parallel to slightly swollen, usually unbranched, the tips irregular; lateral paraphyses inconspicuous, to c. 25 µm long; columellar structures absent. Epihymenium hyaline or becoming brownish, usually with fine grayish-brown granules and small crystals. Asci 4~8 spored. Ascospores transversely septate, oblong-fusiform to clavate, the ends ± rounded to acute, hyaline, post mature or decaying ascospores brownish, faintly to moderately amyloid, 30~50 × 7~10 µm, with 8~16 locules; locules ± rounded to slightly angular, rarely subglobose to lentiform; end cells hemispherical to conical; septa thick, regular; ascospore wall thick, thinly halonate, often crenate. Pycnidia not seen.

Chemistry

Spot test reactions: all negative. Secondary metabolites: none detected.

Ecology

At the collection site the species is found growing over Acer bark at an altitude of 798 m.

Geographical distribution

Africa, North and South America, Australia, New Zealand, Pacific region, India, Japan, Java and Philippines (Awasthi 1991; Frisch 2006; Mangold et al. 2009; Matsumoto 2000; Riddle 1923; Salisbury 1975).

Remarks

The species is characterized by thin, ecorticate, whitish thallus; mostly small, ±emergent ascomata with a free proper exciple; small transversely septate, hyaline, I+ purplish-blue ascospores with a crenate surface and the absence of secondary metabolites. It is frequently confused with T. pseudosubtile Mangold, T. diplotrema Nyl. and T. euphorbiae A. Frisch. T. pseudosubtile differs in having hyaline spores that never turn brown on maturity and restricted Australian distribution. T. diplotrema has larger ascospores with thick lateral walls [1418 loculate and 50~70 × 7.5~10 µm in size] while, T. euphorbiae has thin-walled I-ascospores and produces stictic or hypostictic acids in the thallus.

Specimen examined

South Korea, Gangwon Prov., Mt. Sorak, N 38° 05' 270", E 128° 25' 131", alt. 798 m, on Acer bark, 25 May 2009, Y. Joshi & X. Y. Wang 090921 (KoLRI).

Verrucaria muralis Ach. (Fig. 1C, D)

Meth. Lich.: 115 (1803).

Diagnostic characteristics

Thallus saxicolous, epilithic, olive green to pale brownish, dull, epruinose, continuous to irregularly rimose, thin to ± thick, with an indistinct margin and usually without a visible prothallus, areoles subangular to irregular, 0.15~0.35 mm wide. Upper cortex indistinct, thin, epinecral layer absent, algal layer paraplectenchymatous, continuous, 50~75 µm thick, algal cells densely packed, medulla of loose hyphae, with inspersed substrate grains and crystals, colourless. Vegetative propagules absent.

Ascomata perithecia, sessile to semi-immersed, brownish black, dome shaped, emergent portion naked, ostioles inconspicuous to excavate. Exciple subglobose, 0.25~0.35 mm wide, colorless to pale brownish. Involucrellum extending down to middle part of the perithecium, slightly spreading away from the exciple, 30~50 µm thick, slightly thinning downwards. Periphyses sparsely branched and anastomosing. Asci 8-spored. Ascospores hyaline, simple, ellipsoid, 18~22 × 8~10 µm. Pycnidia not seen.

Chemistry

Spot test reactions: all negative. Secondary metabolites: none detected.

Ecology

At the collection site the species was found growing over calcareous rocks in dry and shady regions at an altitude of 1222 m.

Geographical distribution

Eurasia, Japan (Harada 1996), Taiwan, North Africa, North America, New Zealand, Australia, and the Sonoran Desert (Breuss 2007; Fröberg 1989; van Herk and Aptroot 2004).

Remarks

The species is characterized by epilithic, olive brown thallus, medium-sized and partly immersed perithecia with involucrellum enclosing half of the exciple. The only other species of Verrucaria known from South Korea (V. glaucina Ach.) differs in having narrowly elliptical, smaller ascospores (10~20 × 5~9 µm). V. calkinsiana Servít, differs in having smaller perithecia with darker exciples and thicker, more deeply-reaching involucrella, whereas V. nigrescens Pers. differs in having a thicker thallus with a black basal layer.

Specimen examined

South Korea, Gangwon Prov., Mt. Sorak, N 37° 18' 367", E 128° 56' 766", alt. 1222 m, on rocks, 15 May 2009, Y. Joshi & X. Y. Wang 090417 (KoLRI).