Thelotrema isidiosum S. Joshi, Upreti & Hur, 2018

Joshi, Santosh, Upreti, Dalip K., Bawingan, Paulina A. & Hur, Jae-Seoun, 2018, New species in the family Graphidaceae (Ascomycota: Ostropales) from the Philippines, Phytotaxa 345 (2), pp. 152-158 : 153-156

Thelotrema isidiosum S. Joshi, Upreti & Hur spec. nov. ( Fig 2A–C )

Mycobank MB824345

Differing from Thelotrema isidiophorum in that the thallus produces transversely septate ascospores and salazinic acid as a secondary compound.

Type:— THE PHILIPPINES. IIocos Norte: Luzón Island, Adams, Mt. Mabolo, 18°26’26.3’’ N, 120°53’27.1’’ E, alt. 473 m, on bark, January 2015, Paulina A. Bawingan PH 150039 (holotype: KoLRI).

Thallus corticolous, crustose, green to greenish-grey, continuous, glossy, isidiate, 50–90(–100) μm thick; cortex loose, 10–15 μm thick; algal layer trentipohlioid, 10–25 μm thick; medulla white crystalline, 30–50 μm; isidia cylindrical, branched, coralloid, 0.4–0.6 × 0.09–0.1 mm; prothallus dark brown.

Apothecia porinoid, sessile, barrel-shaped, dispersed, 1–2 mm diam.; pore widely open, 0.2–0.4 mm in diam.; disc flesh colored, epruinose, partly covered by proper exciple, deeply immersed; thalline margin distinct, entire, embedded with crystals, 120–220 μm thick; proper exciple pale brown, reddish-brown to brown, free, denticulate apically; 120–160 μm thick, embedded with crystals, separated from the thalline margin by a narrow split (double margin); epihymenium greyish, crystalline, 15–25 μm high; hymenium hyaline, clear (lacking oil-droplets), conglutinate, resting deep inside proper exciple, 160–260 μm high; paraphyses unbranched, parallel, 1–2 μm thick; subhymenium hyaline, indistinct; asci clavate, 8-spored, (210–)213.9−224−234(–236) × (26.5−)27.3−30–33.3(–34) μm (n =10), non-amyloid; ascospores hyaline, fusiform, transversely septate, 15–22-locular with ± wavy spore wall, endospore 5–6 μm thick, (95–)98.2−101.4−104.6(–105.8) × (15−)15.6−16.7–17.8(–18) μm (n =40), amyloid.

Chemistry:— K+ red, PD + yellow-orange, C–; salazinic acid detected by TLC.

Etymology:— The epithet refers the isidiate thallus of the new taxon.

Distribution and Ecology:— The new taxon is described only from the type locality in the Philippines, where it was growing in association with Leiorreuma exaltatum (Mont. & Bosch) Staiger , Pallidogramme chrysenteron (Mont.) Staiger, Kalb & Lücking , Platythecium pyrrhochroum (Mont. & Bosch) Z. F. Jia & Lücking , Sarcographa labyrinthica (Ach.) Müll. Arg. , and species of Pertusaria DC. and Porina Ach. on thin barked trees.

Remarks:— The new taxon is distinguished in having coralloid isidiate, loosely corticate thallus producing salazinic acid, sessile, barrel-shaped apothecia with wide pores and double margin, hyaline to pale brown proper exciple internally lined by peripysoids, 8-spored asci and transversely septate ascospores with thick endospore. The new species differs from and does not seem close to any of the species in Thelotrema Acharius (1803: 130) . The isidiate thallus in the genus is rare, and found only in T. isidiophorum (Kremp.) Zahlbr , which also has sessile apothecia, but is clearly distinguished in having a verrucose thallus containing stictic acid and large, muriform ascospores, 180–300 × 15–25 μm ( Rivas Plata et al. 2010: 175). Thelotrema isidiosum shares some taxonomic characteristics with Thelotrema porinoides Mont. & Bosch. , T. heladivense Weerakoon, Jayalal & Lücking , T. weberi Hale and T. subweberi Sipman. Thelotrema porinoides with transversely 13–25(–27)-septate, amyloid ascospores of 40–150(–170) × 15–22 μm is close, but differs from the new taxon in having a non-isidiate thallus containing the stictic acid chemosyndrome ( Mangold et al. 2009: 393; Rivas Plata et al. 2010: 173). Thelotrema heladivense also produces transversely, up to 15- septate ascospores measuring 80–100 × 12–15 μm, but is clearly separated in that the thallus lacks isidia and contains norstictic acid with unknown compounds, as well as in having weakly amyloid ascospores ( Weerakoon et al. 2015: 84). Thelotrema weberi and T. subweberi with barrel-shaped apothecia are comparable to the new taxon in having strongly amyloid ascospores, but both the former species are distinct in producing muriform ascospores and norstictic acid in the thallus ( Rivas Plata et al. 2010: 175).

Additional specimen examined:— THE PHILIPPINES. IIocos Norte: Luzón Island, Adams, Mt. Mabolo, 18°26’49.5’’ N, 120° 54’ 58.6’’ E, alt. 393 m, on bark, January 2015, Paulina A. Bawingan PH 150064 (KoLRI).

Figures

FIGURE 2. Thelotrema isidiosum (holotype). A. Habit. B. Section through apothecia showing free and hyaline excipulum. C. Ascospores. Scales: A = 2 mm, B = 1 mm, C = 100 μm.