Thelotrema pachysporoides Dantas, Lucking & M. Caceres 2017, sp. nov.
Creators: name: Dantas, Jaciele De Oliveira
name: Alves, Elaine Santos
name: Lücking, Robert
name: Cáceres, Marcela Eugenia Da Silva
Publisher: name: Zenodo
Year: 2017
Subjects: Biodiversity
Taxonomy
Fungi
Ascomycota
Lecanoromycetes
Ostropales
Graphidaceae
Thelotrema
Thelotrema pachysporoides

description: Thelotrema pachysporoides Dantas, Lücking & M. Cáceres, sp. nov. Fig. 1I–L   
Mycobank No.: MB 822331.  
 Diagnosis: Differing from Thelotrema pachysporum in the small ascospores and from T. fuscosubtile in the ecorticate thallus and smaller, distinctly brown ascospores.   
 Type: BRAZIL. SERGIP E: Fazenda Santa María da Lage; 10º44’37” S, 38º05’44” W, 390 m; isolated remnant of Caatinga vegetation, on tree bark; 28 January 2015, J. Dantas (ISE 30802 — holotype); ibid., J. Dantas (ISE 30801 — paratype).   
 Etymology: The epithet refers to the similarity with Thelotrema pachysporum.   
 Description: Thallus corticolous, epiperidermal, up to c. 5 cm diam., continuous; surface uneven, white-grey to pale yellowish grey; prothallus absent. Thallus in section 50–100 μm thick, ecorticate or in part with a loose cortex, 5–10 μm thick, with thick photobiont layer 40–80 μm thick, interspersed with clusters of calcium oxalate crystals. Photobiont Trentepohlia; cells rounded to irregular in outline, in irregular groups, yellowish green, 8–12 × 6–9 μm. Ascomata rounded, erumpent to prominent, 0.25–0.4 mm diam., 0.15–0.2 mm high; disc partially covered by 0.15–0.25 mm wide pore, grey-brown, thickly white-pruinose; proper margin thin, entire, separated from the thalline margin by a narrow split, forming an indistinct, white rim around the disc; thalline margin thick, smooth to uneven, white-grey to pale yellowish grey. Excipulum entire, pale yellow, 10–20 μm wide, paraplectenchymatous, separated from covering thalline layer by a split; laterally covered by algiferous thallus, 40–60 μm thick; columella absent; hypothecium prosoplectenchymatous, 10–20 μm high, hyaline; hymenium 90–100 μm high, hyaline, clear; epihymenium 5–10 μm high, grey-granular, granules not soluble in K. Periphysoids present, 20–30 μm long; asci fusiform, 70–80 × 15–20 μm. Ascospores 8 per ascus, ellipsoid, 7–13-septate, 25–35 × 7–10 μm, 3–4 times long as wide, becoming brown, distoseptate with lens-shaped lumina, I+ weakly violet-blue when immature. Secondary chemistry: No substances detected by TLC.   
Distribution and ecology: Thus far only known from the state of Sergipe in northeast Brazil, growing on tree bark in an isolated Caatinga remnant.  
 Characterization and taxonomic relationships: Thelotrema pachysporoides belongs in the T. monosporum group, characterized by a whitish, ecorticate thallus and brown ascospores (Rivas Plata et al. 2010, 2013). It is most similar to T. pachysporum Nyl. (hence the specific epithet), which differs in the larger ascospores (35–75 × 9–13 μm). The Australian Thelotrema fuscosubtile Mangold, Lücking & Lumbsch (Mangold et al. 2014) is partially (loosely) corticate, has ascomata with a thicker thalline margin and very distinct proper margin, and produces slightly larger ascospores (35–50 × 7–10 μm), which remain hyaline for a long time and eventually become pale brown.
description: Published as part of Dantas, Jaciele De Oliveira, Alves, Elaine Santos, Lücking, Robert & Cáceres, Marcela Eugenia Da Silva, 2017, Three new species of Graphidaceae (lichenized Ascomycota) from the semi-arid region of northeast Brazil, pp. 289-294 in Phytotaxa 331 (2) on pages 292-293, DOI: 10.11646/phytotaxa.331.2.13, http://zenodo.org/record/13721716