Rhytidhysteron esperanzae Cobos-Villagran , R.Valenz. & 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 esperanzae Cobos-Villagran, R.Valenz. & Raymundo sp. nov

Fig. 3

Diagnosis.

Different from most Rhytidhysteron species by having greyish-green ascomata with greenish-grey to yellow epithecium in the presence of KOH, and large and wide ascospores (45-47 × 17-19 μm).

Type.

Holotype: Mexico. Oaxaca, Sierra de Juárez, Chinantla, Santiago Comaltepec Municipality , La Esperanza , Carretera Oaxaca-Tuxtepec Km 51, 17°37'55"N, - 96°22'01"W, 1600 m a.s.l., 23 May 2017, T. Raymundo 6579 (ENCB). GenBank: LSUMW9394457, ITSMZ056795 .

Etymology.

The epithet refers to the locality "La Esperanza" where the species was found.

Description.

Ascomata hysterothecial to apothecial, (2-)3-4.5 mm long, (1.2-)2-3 mm wide, (1-)1.7-2.4 mm high, superficial, solitary, rarely gregarious, boat-shaped hysterothecia, elongated, straight or flexuous, with sharp ends, opening in a discoid shape when ripe or with humidity, exposing the hymenium, taking the apothecial shape of 3-4 mm in diameter, brown (6D7), dull-green (30E4) to black. Margin involute, perpendicularly striate, greyish green (30C4) to dull green (30D4). Exciple integrated in two layers, the first carbonaceous, glabrous, 60-220 μm wide, thinning in the apical part, the middle part and the base are thicker, composed of pseudoparenchymal cells of textura globulosa-angularis (isodiametric cells), 11 × 10 μm, thick-walled, 3 μm wide, the second slightly pigmented to hyaline, thin-walled. Pseudoparaphyses up to 4 μm wide, filamentous, capitate, apical part wider, straight, hyaline, with a septum, enclosed in a gelatinous matrix, strongly anastomosed above the asci. Epithecium dark green (30F4) to black, becoming yellow (2A7) in the presence of 10% KOH. Asci (250-)265-270 × (18-)19-20 μm, bitunicate, cylindrical, rounded apex, hyaline, uniseriate, octosporic, thick-walled, with a short pedicel. Ascospores of (42-)45-47(-49) × (15-)17-19(-23) μm, (x̄= 45 × 17.2 μm, n = 30), ellipsoidal to spindle-shaped, rounded or pointed at both ends, reddish-brown to brown when mature, with three transverse septa, constricted at the septa, thick-walled and smooth.

Distribution.

Known from a single locality in a forest in La Esperanza, Mexico.

Ecology.

Dead stems and twigs in tropical cloud forest dominated by Oreomunnea mexicana Standl. J.-F. Leroy ( Juglandaceae ).

Specimens examined.

Mexico. Oaxaca. Sierra de Juárez, Santiago Comaltepec Municipality, La Esperanza, Carretera Oaxaca-Tuxtepec Km 51, 17°37'55"N, - 96°22'01"W, 1600 m a.s.l., 22 May , 2017, R. Valenzuela 17206 (ENCB) ; 23 May 2017, A. Cobos-Villagrán 498 (ENCB); 25 May 2017, E. Campero 3 (ENCB), 30 April 2018, A. Cobos-Villagrán 1119 (ENCB), A. Gay AG30041814 (ENCB).

Notes.

Rhytidhysteron esperanzae , is characterised by a brown, dull-green to black exciple and dark green to black epithecium that, in reaction with 10% KOH, changes to yellow colouration. This colouration with KOH is very different than those of of R. rufulum and R. neorufulum which are magenta and violet, respectively. R. esperanzae have larger ascospores than R. rufulum (22.4-30.4 × 8-9.6 μm) and R. mexicanum (34-40 × 10-12 μm). Ecologically, this new species grows in a tropical cloud forest dominated by Oreomunnea mexicana Standl. J.-F. Leroy ( Juglandaceae ).

Figures

Figure 3. Rhytidhysteron esperanzae (Holotype, T. Raymundo 6579) A appearance of ascomata apothecial on host B ascomata apothecial close-up, greyish-green to dull green and striated margin and dark green to 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 isodiametric cells (textura globulosa-angularis), close-up E asci F ascospores.