Introduction
The cosmopolitan genus Graphis Adans. (Graphidaceae, Ostropales, Ascomycota) comprises c. 330 species worldwide (Lücking Reference Lücking2009; Lücking et al. Reference Lücking, Archer and Aptroot2009). To clarify the taxonomy of the genus, a comprehensive study was conducted (Lücking et al. Reference Lücking, Archer and Aptroot2009), which included in Graphis species with rounded to lirellate or pseudostromatic ascomata, mostly carbonized proper exciple, non-amyloid, functionally unitunicate asci with apical wall thickening, hyaline and amyloid, trans-septate to muriform ascospores with lens-shaped lumina, and Trentepohlia as photobiont (Staiger Reference Staiger2002; Lücking et al. Reference Lücking, Archer and Aptroot2009).
South Korea has a high diversity of lichen-forming fungi in the southern regions of the country (Hur et al. Reference Hur, Harada, Oh, Lim, Kang, Lee, Kahng, Kim, Jung and Koh2004, Reference Hur, Koh and Harada2005). However, the genus Graphis is poorly studied and previous collections seem to have, to date, neglected this genus from the South Korean mycota, as indicated by only 13 species being recorded from different provinces (Hur et al. Reference Hur, Koh and Harada2005): Graphis anfractuosa (Eschw.) Eschw., G. cervina Müll. Arg., G. cognata Müll. Arg., G. dupaxana Vain., G. handelii Zahlbr., G. intricata Eschw., G. proserpens Vain., G. intermediella Stirt. [=G. rikuzensis (Vain.) M. Nakan.] and G. scripta (L.) Ach., as well as the four recently added species G. aperiens Müll. Arg., G. flavopalmicola Y. Joshi et al., G. jejuensis K. H. Moon, and G. psunodae Zahlbr. (Joshi et al. Reference Joshi, Lücking, Yamamoto, Wang, Koh and Hur2010; Moon et al. Reference Moon, Nakanishi and Kashiwadani2012).
In the course of an ongoing survey of crustose lichens from sub-temperate regions of the country and material preserved in the herbarium of the Korean Lichen Research Institute (KoLRI), an interesting and novel specimen of Graphis was identified. The species is characterized by an olive-green to ±brownish green, rather thick thallus, complete thalline margin, black, lirellate ascomata, concealed disc, entire labia, completely carbonized proper exciple, mostly trans-septate to submuriform ascospores and a saxicolous habitat.
Materials and Methods
The material was examined with a SMZ-168 dissecting microscope (China) and BX-50 compound microscope (Olympus, Tokyo, Japan). Thin, hand-cut sections were observed on material mounted in water, 10% KOH solution, Lugol's iodine (I) and lactophenol Cotton Blue (LB). All measurements were taken under higher magnification of ×40 and ×1000 prior to application of KOH. Lichen substances were identified by thin-layer chromatography (solvent systems C and A) and colour spot tests as described by Orange et al. (Reference Orange, James and White2010).
The Species
Graphis koreana S. Joshi & Hur sp. nov.
MycoBank No.: MB 803015
Similar to Graphis assimilis, but differing in having a green thallus, complete thalline margin and saxicolous habit.
Type: South Korea, Jeollanam-do, Goheung-gun, Jeomam-myeon, Mt Palyeongsan, Yuyeongbong, 34°37·824′N, 127°25·701′E, alt. c. 465 m a.s.l., on rocks, Y. Joshi, S. Jeon & G. S. Han 100294 (KoLRI–holotype).
Graphis koreana (holotype). A, habitat; B, habit; C, ascomata. Scales: A=3 cm; B & C=1 mm.
Graphis koreana (holotype). A, completely carbonized exciple; B, ascus with ascospores; C, ascospores (note the distinct halo in the immature ascospore, arrow). Scales: A=100 µm; B=50 µm; C=20 µm.
Thallus saxicolous, epilithic, crustose, corticate, continuous, rimose-cracked, smooth to rough, epruinose, dull, olive-green to ±brownish green, 300–500 µm thick in cross-section. Cortex 20–30 µm thick. Photobiont layer up to 100 µm thick. Medulla whitish to creamish, up to 400 µm thick with inclusions of crystals. Prothallus indistinct to blackish.
Ascomata lirelliform, immersed to ±erumpent (scarcely raised above the thallus). Lirellae completely covered by thalline margin (10–12 µm thick), short to 5 mm in length, ends mostly rounded. Labia entire, greyish to blackish, covered by thin cortex. Disc slit-like, epruinose, concealed. Proper exciple entire, completely carbonized, convergent, ±round, thin to basally thick, 30–60 µm wide. Epihymenium indistinct to absent. Hymenium hyaline, not inspersed, 100–120 µm high, I−; paraphyses simple, rather lax, apically granulate, ±conglutinate, 1–2 µm thick. Hypothecium hyaline, indistinct to 20 µm high, I−. Ascus clavate, 8-spored, with distinct stipe (up to 30 µm long), 130–135×20–27 µm, I−. A scospores hyaline, clavate to ellipsoid with rounded ends, mostly transversely 9–12-septate with one longitudinal septum in the middle locules, (33–)35–45(–50) × 10–12 µm, locules angular with rounded ends, immature ascospores distinctly halonate, halo up to 6 µm thick, I+ violet to blue.
Etymology
The specific epithet refers to the country from where the new taxon is being described.
Chemistry
Thallus and medulla K+ yellow turning red, P+ yellow-orange, C−, KC−; norstictic acid detected by TLC.
Distribution and ecology
The new species is known only from the type locality (Mt Palyeongsan, Jeollanam-do) in South Korea, where it was widely dispersed on rocks and collected at an altitude of c. 465 m. Mount Palyeongsan is a mountain range of steep and undulating geographical forms reaching an altitude of around 600 m. The type locality is situated in the southern part of the country and characterized by granite and gneiss rocks with mixed tree vegetation of spruce and Korean pine. Other species of lichens reported from the locality are Porpidia albocaerulescens (Wulfen) Hertel & Knoph, Cladonia scabriuscula (Delise) Leight., Caloplaca cinnabarina (Ach.) Zahlbr. and several members of Lecanoraceae, Parmeliaceae, Stereocaulaceae and Verrucariaceae.
Remarks
The new species is well characterized by a green (dark green to brownish green or bluish green), thick thallus, lirellae with complete thalline margin and entire labia, completely carbonized, convergent proper exciple, transversely septate ascospores with one longitudinal septum frequently in the middle lumina, and the presence of norstictic acid as a secondary compound.
Graphis assimilis Nyl. closely resembles G. koreana in having entire labia, short, sparsely branched lirellae, 30–45 µm long ascospores, and a thallus containing norstictic acid, but differs in that it has ascomata with a lateral thalline margin and hence shows a different lirellae morphology (lineola-morph). Furthermore, G. assimilis is corticolous and has a white thallus, while the new species grows on rocks with a green thallus. Graphis koreana is also comparable to G. caesiocarpa Redinger in having a concealed disc, entire labia, transversely septate ascospores, and norstictic acid, but G. caesiocarpa has lirellae of the caesiella-morph (with pruina), 5–7 septate, small ascospores 15–20×5–6 µm in size, and lirellae with a lateral thalline margin (Lücking et al. Reference Lücking, Archer and Aptroot2009). Graphis kollaimalaiensis Adaw. & Makhija, another similar species with a concealed disc and entire labia, has somewhat larger ascospores (c. 45–70 µm) and a different lirellae morphology (hossei-morph). Similarly, G. assamensis Nagarkar & Patw. is separated from the new species in having erumpent lirellae and a thallus that produces stictic and salazinic acids as chemical compounds.
Among the Graphis species reported from Korea, Graphis aperiens shares some characteristics with G. koreana, such as a completely carbonized excipulum, transversely septate ascospores, and the presence of norstictic acid, but differs in having an exposed, white-pruinose disc and lirellae with lateral thalline margin (scripta-morph), inspersed hymenium, and small ascospores of 20–35 µm with less transverse septa. Graphis cervina, the only saxicolous species previously reported from South Korea, has lirellae of the lineola-morph, small ascospores 15–25 µm long, and produces stictic acid in addition to norstictic acid. Moreover, the new taxon frequently has a vertical septum in the middle locules.
Among species with muriform ascospores, Graphis koreana seems to be closest to G. cremicolor (H. Magn.) Lücking & Archer and G. nadurina Aptroot, which have 20–50 µm long ascospores and contain norstictic acid. Graphis cremicolor also agrees in the saxicolous habit, but it differs in having lirellae with a lateral thalline margin, whereas G. nadurina has short unbranched lirellae (cleistomma-morph) and 2-spored asci.
This work was supported by a grant from the Korea National Research Resource Center Program and the Korean Forest Service Program (KNA 2012) through the Korea National Arboretum. SJ thanks Drs Robert Lücking, Alan W. Archer and André Aptroot for providing many discussions and valuable comments on the species.
