Rhytidhysteron cozumelense Cobos-Villagran , R. Valenz., Hdz-Rdz., Calvillo-Medina & Raymundo, 2021

Cobos-Villagran, Aurora, Valenzuela, Ricardo, Hernandez-Rodriguez, Cesar, Calvillo-Medina, Rosa Paulina, Villa-Tanaca, Lourdes, Mateo-Cid, Luz Elena, Perez-Valdespino, Abigail, Martinez-Gonzalez, Cesar Ramiro & Raymundo, Tania, 2021, Three new species of Rhytidhysteron (Dothideomycetes, Ascomycota) from Mexico, MycoKeys 83, pp. 123-144 : 123

Rhytidhysteron cozumelense Cobos-Villagran, R. Valenz., Hdz-Rdz., Calvillo-Medina & Raymundo sp. nov

Fig. 2

Diagnosis.

Differs from Rhytidhysteron rufulum in its host ( Bignoniaceae ), size of ascomata (2.5-3.5 × 1.1-1.5 × 1.0-1.9 mm), asci (182-191 × 12-13 μm) and its reaction with KOH being faster (one to five seconds).

Type.

Holotype: Mexico. Quintana Roo, Cozumel Municipality, San Gervasio Chen-tuk archaeological zone, 20°29'50"N, - 86°50'39"W, 0 m a.s.l., 21 January 2018, A. Cobos-Villagrán 951 (ENCB), on Tabebuia rosea DC. ( Bignoniaceae ), GenBank: LSUMW9394459, ITSMZ056797, tef1 MZ457338 .

Description.

Ascomata hysterothecial to apothecial 2.5-3.5 mm long, 1.1-1.5 mm wide, (0.8)1.0-1.9 mm high, erumpent, solitary, boat-shaped hysterothecia, subglobose, elongated, compressed in the apex, with conspicuous longitudinal groove or cleft and becoming lenticular when mature or exposed to moisture, black, carbonaceous when dry. Margin involute, smooth to perpendicularly slightly striated, black. Exciple integrated in two layers, the first carbonaceous, glabrous, 45-100 μm thick, wide at the base, composed of pseudoparenchymal cells of textura prismatica (iso-radiating cells), thick-walled, the second composed of cells hyaline, thin-walled. Pseudoparaphyses up to 2.5 μm wide, filamentous, capitate, hyaline, septate, enclosed in a gelatinous matrix, strongly anastomosed above the asci. Epithecium reddish brown (8F7) when fresh, black in old specimens or when dry, becoming greyish magenta (13B5) in the presence of 10% KOH. Asci 182-191 × 12-13 μm, bitunicate, cylindrical, hyaline, uniseriate, octosporic, thick-walled, with a sinuous base. Ascospores 26-29(-31) × 9-11 (-13) μm, (x̄= 28 × 10.2 μm, n = 30), ellipsoidal to fusiform, rounded at both ends, dark brown in colour with three transverse septa, with a thick and smooth wall.

Distribution.

Known from a single local Island in the Cozumel Biosphere Reserve, Mexico.

Ecology.

Dead twigs of Tabebuia rosea DC. ( Bignoniaceae ).

Etymology.

The epithet refers to the Island in the Cozumel Biosphere Reserve where the species was found.

Specimens examined.

Mexico, Quintana Roo, Cozumel Municipality, San Gervasio Chen-tuk archaeological zone, 20°29'54"N, - 86°50'43"W, 13 m a.s.l., 21 January 2018, T. Raymundo 7321, R. Valenzuela 17985 (ENCB); 17 June 2018, A. Cobos-Villagrán 1838 (ENCB) .

Notes.

Rhytidhysteron cozumelense is characterised by black ascomata with a reddish brown epithecium and a smooth to slightly striated margin that, in reaction with 10% KOH, changes to greyish magenta. R. mesophilum has a similar reaction in KOH, but with several tones of green in the hysterothecia, a reddish orange to orange red epithecium and a perpendicularly striate with irregular slits and yellowish green pruina in margin. R. rufulum has a magenta reaction in KOH and strongly striated margin. Tabebuia rosea is reported as a new host for a Rhytidhysteron species.

Figures

Figure 2. Rhytidhysteron cozumelense (Holotype, A. Cobos-Villagran 951) A appearance of ascomata hysterothecial and apothecial on host B ascomata apothecial close-up, striated margin and black epithecium C-F microscopical features stained with alcohol (70 %) and KOH (10 %) reagent C ascomata apothecial cross-section with alcohol (70 %) D exciple of iso-radiating cells (textura prismatica), close-up E asci F ascospores.