The genus Schismatomma Flot. & Körb. ex A. Massal. was described by Massalongo (Reference Massalongo1852) containing five species. The genus is generally characterized by a whitish thallus containing calcium oxalate crystals, lirellate to short rounded ascomata with a poorly developed thalline margin, a carbonaceous hypothecium, 3-septate fusiform ascospores, and roccellic acid as a secondary metabolite (Tehler Reference Tehler1993a). As a result of recent phylogenetic studies in the Arthoniales, the species in Schismatomma were transferred and segregated under different genera and are now placed in the family Roccellaceae (Ertz & Tehler Reference Ertz and Tehler2011; Ertz et al. Reference Ertz, Tehler, Irestedt, Frisch, Thor and van den Boom2013, Reference Ertz, Sanderson, Coppins, Klepsland and Frisch2019).
The species of Schismatomma described from India were enumerated by Awasthi (Reference Awasthi1965) and included eight species: S. atomellum (Stirt.) Zahlbr., S. cinereum (Müll. Arg.) Zahlbr., S. flavisedellum (Nyl.) Zahlbr., S. glaucomoides (Nyl.) Zahlbr., S. gregantulum (Müll. Arg.) Zahlbr., S. incurvulum (Stirt.) Zahlbr., S. kurzii (Kremph.) Zahlbr. and S. melastigma (Nyl.) Zahlbr. Thor (Reference Thor1990) synonymized the species S. incurvulum under Graphidastra multiformis (Mont. & Bosch) G. Thor., while S. kurzii was transferred to Erythrodecton G. Thor with the new combination Erythrodecton kurzii (Kremp.) G. Thor. Later, Henssen & Thor (Reference Henssen and Thor1998) established a new genus, Pulvinodecton Henssen & G. Thor, and proposed a new combination, P. kurzii (Kremp.) Henssen & G. Thor. Tehler (Reference Tehler1993b) transferred the species S. glaucomoides to Sigridea with the new combination S. glaucomoides (Nyl.) Tehler. In a worldwide monograph of Schismatomma, Tehler (Reference Tehler1993a) accepted only eight species and excluded all five species known from India. The species S. atomellum, S. cinereum and S. gregantulum were placed in the genus Phlyctella Kremp. without proposing any new combinations. Schismatomma melastigma was provisionally placed in the genus Arthonia Ach. while S. flavisedellum was transferred to the genus Lecanactis Körb. with a new combination, Lecanactis flavidosella (Nyl.) Tehler.
The existence of Schismatomma in India is now doubtful. However, Singh & Sinha (Reference Singh and Sinha2010) retained the species S. atomellum, S. cinereum, S. gregantulum and S. melastigmum in ‘Indian Lichens: An Annotated Checklist’, following Awasthi (Reference Awasthi2000). They stated that a species is retained until its taxonomic status is resolved. During the ongoing revisionary studies on the Arthoniales in India, type specimens of all the above species from India were examined. The species S. atomellum, S. cinereum and S. gregantulum were found to have similar morphological, anatomical and chemical characters to the genus Phlyctis (Wallr.) Flot. The present study therefore agrees with the observations mentioned in the monograph on Schismatomma by Tehler (Reference Tehler1993a) where the above species were treated under Phlyctella, but no new combinations were proposed. At present, the genus Phlyctella is a heterotypic synonym under Phlyctis. Due to recent phylogenetic studies, taxonomic changes and the transfer of Phlyctomia A. Massal., Phlyctella and Phlyctidia Müll. Arg. to Phlyctis, the genus has become more heterogeneous with several variable characters. Phlyctis is characterized by a crustose to sub-leprose thallus, erumpent ascomata, mostly remaining immersed, sometimes raised, single or clustered, often with a raised margin of thallus fragments, a usually pruinose disc, true exciple not obvious or rudimentary, paraphyses mostly unbranched, asci 1, 2, 4 or 8-spored with transversely septate to muriform hyaline ascospores, and a wide variety of secondary metabolites (e.g. members of the norstictic acid, stictic acid, or psoromic acid aggregates) or lacking lichen substances (Joshi & Upreti Reference Joshi and Upreti2013; Muscavitch et al. Reference Muscavitch, Lendemer and Harris2017). Accordingly, morphological, anatomical and chemical characters of the types of Schismatomma atomellum, S. cinereum and S. gregantulum suggest that they should be assigned to the genus Phlyctis. Interestingly, these three species are conspecific with the recently described Graphidastra himalayana Jagadeesh & G. P. Sinha from West Bengal (Jagadeesh Ram & Sinha Reference Jagadeesh Ram and Sinha2010), and the earlier known Phlyctis himalayensis (Nyl.) D. D. Awasthi (≡Phlyctella himalayensis Nyl.) from Sikkim (Awasthi Reference Awasthi2000). Platygrapha atomella Stirt. (≡S. atomellum) has priority over the other four names following the rule of priority (Art. 11.4; Turland et al. Reference Turland, Wiersema, Barrie, Greuter, Hawksworth, Herendeen, Knapp, Kusber, Li and Marhold2018). Thus, the new combination Phlyctis atomella (Stirt.) S. Joseph et al. is proposed and the other four species are synonymized under it.
Schismatomma melastigma belongs to Arthoniaceae due to its Arthonia-type ascus and this agrees with the observations by Tehler (Reference Tehler1993a). However, spores were not seen in the type material of S. melastigma procured from H-NYL, which is in a very poor condition (type: India, Calcutta, 1866, S. Kurz, H-NYL 4628!) and other parts of the type preserved at M were not available for study. Recently, Goni & Sharma (Reference Goni and Sharma2016) reported Schismatomma galactinum (Leight.) Zahlbr. as a new record from the state of Jammu and Kashmir. Study of the specimen revealed that the Indian specimens belong to the genus Opegrapha s. lat.
Phlyctis atomella (Stirt.) S. Joseph, G. P. Sinha & S. Nayaka comb. nov.
MycoBank No.: MB 835457
Platygrapha atomella Stirt., Proc. Roy. Philos. Soc. Glasgow 11, 317 (1879).—Schismatomma atomellum (Stirt.) Zahlbr., Cat. Lich. Univ. 2, 553 (1924); type: India, Nilgiris [‘Neilghiri’], D. G. Watt s. n. (BM—lectotype!).
Graphidastra himalayana Jagadeesh & G. P. Sinha, Geophytology 39(1), 83 (2010); type: India, West Bengal, Darjeeling district, Neora Valley National Park, Aloobari, secondary rainforest, on bark of Eurya acuminata, 27°07′31.7″N, 88°43′03.9″E, elev. 2484 m, 17.05.2008, Jagadeesh Ram 4360 (BSA—holotype!; CAL—isotype!), syn. nov.
Platygrapha cinerea Müll. Arg., J. Linn. Soc., Bot. 29, 224 (1892).—Schismatomma cinereum (Müll. Arg.) Zahlbr., Cat. Lich. Univ. 2, 555 (1924); type: India, Manipur [‘Munipur’], G. Watt 6980 (BM—holotype!), syn. nov.
Platygrapha gregantula Müll. Arg., J. Linn. Soc., Bot. 29, 223 (1892).—Schismatomma gregantulum (Müll. Arg.) Zahlbr., Cat. Lich. Univ. 2, 558 (1924); type: India, Manipur [‘Munipur’], G. Watt s. n. (BM—isotype!), syn. nov.
Phlyctella himalayensis Nyl., Lich. Nov. Zel., 3 (1888).—Phlyctis himalayensis (Nyl.) D. D. Awasthi, Lichenol. Indian Subcontinent, 15 (2000); type: India, Himalaya, Sikkim, reg. temp., 7000 ft, Hook. & Thomson 2052 (H-NYL 22302—holotype, image!), syn. nov.
(Fig. 1)
Fig. 1. Phlyctis atomella, habitus (type of Platygrapha atomella). Scale = 1 mm. In colour online.
Thallus corticolous, up to 50 μm thick; surface pale yellowish, greyish, whitish, smooth to minutely verruculose, cracked to rimose-like, matt. Border line dark brown, c. 0.2 mm wide. Photobiont Trentepohlia.
Ascomata rounded to rarely elongated, solitary or in group of 3–7, immersed to emerged, 0.3–0.6 mm diam., thalline margin thin to thick, 15–57 μm, concolorous with the thallus, rarely detaching from disc by a slit, sometimes giving a verrucose appearance; disc black, plane to concave, white pruinose to epruinose; excipulum thin to rudimentary, 10–20 μm, with pale brown to brownish hyphae, K+ slightly olivaceous; epihymenium pale brownish, 13–25 μm thick, K+ slightly olivaceous, I−; hymenium hyaline, not inspersed, 50–110 μm high, I− or I+ pale blue rapidly changing to orangish red, KI+ pale blue; paraphyses slender, simple, unbranched, c. 1.5 μm wide; hypothecium dark brownish, 8–35 μm thick, K+ slightly olivaceous, I− or I+ pale blue suddenly changing to orangish red, KI+ pale blue; asci cylindric-clavate, 8-spored, ascospores irregularly to spirally arranged, 60–110 × 13–20 μm, walls KI+ blue, tholus KI+ dark blue; ascospores hyaline, fusiform, 7-septate (rarely 5-septate), straight to slightly curved, (33–)45–65(–78) × 4–7 μm, without perispore.
Pycnidia not seen.
Chemistry
Thallus K+ yellow turning red, C−, P+ yellow, UV−. TLC: norstictic acid present.
Additional specimens examined
India: West Bengal: Darjeeling district, Darjeeling Pashok road, elev. 6000 ft, 1967, D. D. Awasthi & M. R. Agarwal 67.110 (LWG-LWU); Neora Valley National Park, Zero Point - PHE Source foot hack, primary rainforest, elev. c. 2250 m, on fallen tree branches, 2007, Jagadeesh Ram 3933 (BSA); Chaudapheri - Zero Point way, primary rainforest, elev. 2379 m, 2008, Jagadeesh Ram 4274 (BSA); Neora riverine forests, primary rainforest, elev. 2250 m, 2010, Jagadeesh Ram 6077 (BSA); Aloobari, secondary rainforest, 27°07′26.9″N, 88°42′44.2″E, elev. 2494 m, on Eurya acuminata, 2008, Jagadeesh Ram 4362 (BSA); ibid., 27°07′30.1″N, 88°42′47.7″E, elev. 2511 m, Jagadeesh Ram 4363; ibid., 27°07′25.7″N, 88°43′05.6″E, elev. 2441 m, 2010, Jagadeesh Ram 6119, 6120, 6121, 6143 (BSA); ibid., 27°07′26.9″N, 88°43′06.2″E, elev. 2465 m, 2010, on Eurya acuminata, Jagadeesh Ram 6125 (BSA).
Acknowledgements
The authors are grateful to the Director, Botanical Survey of India (BSI), Kolkata, and to the Director, CSIR-National Botanical Research Institute (NBRI), Lucknow for providing facilities. The authors thank the curators of BM (The Natural History Museum, London) and H-NYL (Hb. William Nylander, Finnish Museum of Natural History, University of Helsinki, Finland) for the loan of type specimens. The initial stages of the work were carried out in BSI during part of SJ's ‘Flora of India Project’. SJ is also grateful to DST, New Delhi for financial assistance under the INSPIRE Faculty scheme (IFA18-LSPA 124). The authors would also like to thank the two anonymous reviewers for their valuable comments and suggestions to improve the quality of the paper.
Author ORCIDs
Siljo Joseph, 0000-0002-8027-7936.
