Thelotrema megasporum 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 : 156-157

Thelotrema megasporum S. Joshi, Upreti & Hur spec. nov. ( Fig 3A–D )

Mycobank MB824346

Resembles Thelotrema thesaurum , but differs in having 1-spored asci and much larger ascospores (145.8–330 × 35–44.5 μm vs 60–120(– 130) × 20–30 μm in Thelotrema thesaurum ).

Type:— The Philippines. IIocos Norte: Luzón Island, Adams, Mt. Mabolo, 18°27’13.4’’ N, 120°54’45.9’’ E, alt. 361 m, on bark, January 2015, Paulina A. Bawingan PH 150051 (holotype: KoLRI).

Thallus corticolous, crustose, brownish to yellowish-brown, waxy, glossy, continuous, verruculose, undulate (due to bark texture), hard, 300–400 μm thick; cortex distinct 50–60 μm thick; photobiont trentepohlioid, algal layer embedded with large crystals at the base, 50–90 μm thick; medulla white, mostly embedded with large crystals and periderm cells, up to 250 μm thick; prothallus dark brown.

Apothecia porinoid, sessile, barrel-shaped, numerous, dispersed, 0.5–1 mm diam. and 0.6–0.8 mm high; pore widely open, 0.2–0.3 mm diam.; disc flesh colored, mostly covered by proper exciple, white pruinose; thalline exciple distinct, entire, eroded, whitish apically, embedded with periderm cells, 140–170 μm thick; proper exciple hyaline, free, separated from the thalline exciple by a narrow split (double margin), 30–70 μm thick, internally lined by 50–70 μm long distinct periphysoids; epihymenium granular, crystalline, ± greyish, indistinct to 15–20 μm high; hymenium hyaline, clear (lacking oil-droplets), 300–500 μm high; paraphyses unbranched, parallel, 1–2 μm thick; subhymenium indistinct; asci clavate, 1-spored, (290.2–)295.5−321.7−347.9(–350) × (40−)40.7−42.7–44.7(–45) μm (n =32), non-amyloid; ascospores hyaline, fusiform, muticelled, muriform, (145.8–)221.1−273.4−325.7(–330) × (35−)36.6−39.5– 42.4(–44.5) μm (n =32) μm, non-amyloid.

Chemistry:— K+ yellow, PD + yellow, C–; stictic acid associated with traces of cryptostictic and constictic acids detected by TLC.

Etymology:— The epithet is named after the large ascospores of the new taxon.

Distribution and Ecology:— The new species was found only at the type locality in the Philippines, where it was growing luxuriantly with Leucodecton compunctum (Ach.) A. Massal. , Phyllopsora albicans Müll. Arg. , Glaucotrema glaucophaenum (Kremp.) Rivas Plata & Lumbsch , Myriotrema microporum (Mont.) Hale , Ocellularia massalongoi (Mont.) Hale , and a number of unidentified Graphis species.

Remarks:— The new species is characterized by a thick, brownish colored thallus containing stictic acid, sessile, barrel-shaped apothecia with double margins, hyaline proper exciple internally lined by periphysoids, 1-spored asci and hyaline, muriform, large, non-amyloid ascospores. Thelotrema megasporum is most similar to Thelotrema thesaurum Mangold in having a verrucose, thick, waxy thallus that is pale olivaceous to yellowish-brown, containing the stictic acid chemosyndrome, sessile apothecia and muriform, hyaline, non-amyloid ascospores. However, the latter species produces (4–)6–8-spored asci with smaller ascospores measuring 60–120(–130) × 20–30 μm ( Mangold et al. 2009: 404).

Thelotrema conferendum Hale is close to the new taxon in having hyaline and muriform ascospores, and the presence of stictic acid in the thallus, but differs in containing distinctly amyloid ascospores, which are smaller (100– 150 μm long) ( Rivas Plata et al. 2010: 175). Thelotrema rugulatum Nyl. is similar in having a verrucose thallus and muriform, hyaline, non-amyloid ascospores (220 × 45 μm), but clearly separated from the new species in lacking secondary compounds ( Rivas Plata et al. 2010: 176).

The presence of a dense cortex and stictic acid in the new taxon resembles species accommodated in the recently revived genus Asteristion Leighton (1870: 163) , which however, differs in having small ascospores (up to 60 μm long) ( Medeiros et al. 2017: 5). The new species is comparable to Asteristion cupulare (Müll. Arg.) I. Medeiros, Lücking & Lumbsch and A. leucopthalmum (Müll. Arg.) I. Medeiros, Lücking & Lumbsch in producing apothecia with a double margin, as well as hyaline muriform, non-amyloid ascospores, but the latter two species differ in having small ascospores measuring 15–30 × 5–10 μm and 30–60 × 10–15 μm, respectively ( Medeiros et al. 2017: 10).

Additional specimen examined:— The Philippines. IIocos Norte: Luzón Island,Adams, Mt. Mabolo, 18°27’13.6’’ N, 120°54’45.1’’ E, alt. 353 m, on bark, January 2015, Paulina A. Bawingan PH 150056 (KoLRI).

Figures

FIGURE 3. Thelotrema megasporum (holotype). A. Habit. B. Apothecia. C. Section through apothecia showing free and hyaline to reddish brown excipulum. D. Ascospores. Scales: A–B = 1 mm, C = 500 μm, D = 100 μm.