Myriostigma nicobaricum Jagadeesh & G.P. Sinha, 2016

Jagadeesh Ram, T. A. M. & Sinha, G. P., 2016, A world key to Cryptothecia and Myriostigma (Arthoniaceae), with new species and new records from the Andaman and Nicobar Islands, India, Phytotaxa 266 (2), pp. 103-114 : 108

Myriostigma nicobaricum Jagadeesh & G.P. Sinha , sp. nov. ( Figs 1E–F & 2F )

MycoBank No.: MB 817299

Myriostigma with homoiomerous thallus; whitish, raised, rounded, 0.3–0.8 mm diam. ascigerous areas; 8-spored asci; broadly ellipsoid to ovoid, 8–11 × 2–4 septate, 34–48 × 16–22 μm ascospores and confluentic acid.

Type: — INDIA. Nicobar Islands, Little Nicobar Island, Akupa, evergreen forest, 7°22’67.2” N, 93°39’75.6”, alt. 15 m, on Bentinckia nicobarica palm, 7.12.2014, T. A. M. Jagadeesh Ram 4222 (Holotype CAL).

Thallus crustose, corticolous, endoperidermal, firmly attached, orbicular to irregular, 3–10 cm across, whitish grey to greyish brown, ± smooth, effuse, indistinct, lacking isidia and soredia, 24–70 μm thick, homoiomerous, ecorticate, lacking calcium oxalate crystals; prothallus indistinct, sometimes forming a thin black line at borders while bordering other species; photobiont trentepohlioid, cells rounded to oblong, 6–10 × 5–7 μm. Ascomata (ascigerous areas) delimited, whitish, distinctly raised, usually rounded, flat, ± evenly scattered, 0.3–0.8 mm diam. and up to 0.4 mm high, densely pruinose, not covered by photobiont layer. Paraphysoids tightly enclosing the asci, I + pale blue, KI+ blue. Asci frequent, aggregated in whitish ascigerous areas, sometimes externally visible as brownish dots, globose to subglobose, 8-spored, c. 70–80 × 50–60 μm. Ascospores colourless, broadly ellipsoid to ovoid, straight, muriform, 8–11 × 2–4 septate, with ± equal cells, 34–48 × 16–22 μm (n=34). Chemistry: Thallus and ascigerous areas K –, C –, KC–, P –; UV –; I + blue, KI+ blue in patches (section); confluentic acid (major).

Notes: — Myriostigma nicobaricum externally and chemically resembles Myriostigma napoense which is also corticolous, has similar distinctly raised rounded ascigerous areas but differs in its heteromerous thallus and the narrowly ellipsoid rather long ascospores ( Kalb et al. 2012, Ertz et al. 2015). Other species such as M. candidum Kremp. (1874: 22) and M. filicinum (Ellis & Everh.) Frisch & G. Thor (in Frisch et al. 2014: 739) are usually foliicolous and also differ in their chemistry. Myriostigma candidum has 2’- O -methylperlatolic and 2’- O -methylanziaic acid while M. filicinum has perlatolic acid ( Lücking et al. 2006, Frisch et al. 2014). Myriostigma subcandidum (M. Cáceres & Lücking) Frisch & G. Thor (in Frisch et al. 2014: 739), a corticolous species, also has similar ascospores and ascigerous areas, but that lacks lichen substances ( Cáceres 2007).

Distribution and habitat: — Myriostigma nicobaricum is known from the high humid, dense evergreen forests in Great and Little Nicobar Islands of the Nicobar Islands.

Etymology: —The specific epithet refers to its inventory from the Nicobar Islands.

Additional specimens examined: — INDIA. Nicobar Islands, Little Nicobar Island, Akupa, evergreen forest, 7°22’64.4” N, 93°39’75.9” E, alt. 15 m, 7.12.2014, T.A.M. Jagadeesh Ram 4177 (PBL). Great Nicobar Island, Campbell Bay, Rajeev Nagar, evergreen forest, 7°00’64.2” N, 93°54’54.6” E, alt. 25 m, 2.6.2014, T.A.M. Jagadeesh Ram 3406 (PBL).

Figures

FIGURE 1. A. Cryptothecia albomaculans (holotype), part of thallus with white maculiform ascigerous areas. B. C. elata (holotype), part of thallus with white raised ascigerous areas. C. C. elongata (holotype), part of thallus with slightly raised ascigerous areas. D. C. superphyllinica (holotype), part of thallus with white raised ascigerous areas. E. Myriostigma nicobaricum (holotype), part of thallus with white raised ascigerous areas. F. M. nicobaricum (paratype). Scales:A–F=1 mm.

FIGURE 2. A. Cryptothecia albomaculans (holotype), ascospores. B. C. elata (holotype), ascospores. C–D. C. elongata (holotype). C. Ascus. D. Ascospores. E. C. superphyllinica (holotype), ascospores. F. Myriostigma nicobaricum (holotype), ascospores. Scales=20 μm.