Dictyonema duidense V. Marcano, 2022

Marcano, Vicente, 2022, Eight new species of lichenized Basidiomycota in the genera Acantholichen, Cyphellostereum and Dictyonema s. str. (Agaricales, Hygrophoraceae) from northern South America, Phytotaxa 574 (3), pp. 199-225 : 212-213

4) Dictyonema duidense V. Marcano , sp. nov.; ( Fig. 7 )

Mycobank MB#838342

Diagnosis:— Sicut Dictyonema barbatum sed hymenocarpis resupinatis, irregularis differt. Thallus corticola, byssaceus, crassus, pagina areolata, rugosa, hyphis non fibulatis. Hymenium N non reagens. Sporae guttaeformes, hyalinae, non septatae, 7–8 μm longae, 2–4 μm latae.

Type:— VENEZUELA. Amazonas: Alto Orinoco, summit northern Cerro Duida , growing on tree trunks at margin of small tepuian forests, elev. 2100 m, March 1996, L. Galiz & V. Marcano AMA-757 (holotype MER, isotype B, private herb. V. Marcano) .

Etymology:—The epithet refers to the locality where the type specimens were collected.

Description:— Thallus shelf-like, corticolous, byssaceous, filamentous, epiphytic on tree trunks, covering larger areas of the substrate with a thick crust, in irregular, confluent patches up to 35 cm across, composed of densely arranged, dark aeruginous fibrils with distinct interspaces resting on a thick, byssoid, irregularly interwoven medulla (hypothallus), visible as narrow, 0.8–1.1 mm wide marginal zone, strongly contrasting with the aeruginous fibrils. Lobes projecting vertically from the substrate, semicircular, coated, dark blue-green, very broad, 15–25 cm; surface areolate, rugose, with entire, white margins, 1–1.5 cm wide, lacking photobiont filaments; photobiont layer composed of numerous cyanobacterial filaments wrapped in a closed hyphal sheath formed by jigsaw-puzzle-shaped cells; cyanobacterial filaments not branched, composed of 20–25 μm wide and 4–6 μm high, bluish green cells penetrated by tubular fungal hyphae (haustoria). Thallus in section 3–6(–7) mm thick, not forming a distinct photobiont layer and medulla but instead composed of aeruginous fibrils connected at base (underside) to a pale brown, loosely woven hypothallus. Clamp connections absent.

Hymenophore forming irregular, reticulated, resupinate patches dispersed on the underside, with entire margin, whitish, smooth surface; hymenophore composed of a paraplectenchymatous layer connected to loose medullary hyphae; hymenium composed of numerous, palisade-like basidioles and scattered basidia; basidiospores ellipsoid to narrowly drop-shaped, non-septate, hyaline, 7–8 × 2–4 μm.

Chemistry:—Thallus K–, C–, KC–, P–; medulla K–, C–, KC–, P–, N–, ER–; basidiocarp K–, C–, KC–, P–, N–, ER– (n = 6). No lichen compounds detected by TLC.

Distribution and Ecology:— Dictyonema duidense is found growing as an epiphyte on tree bark in altotepuian forests at 1500–2100 m. It is known only from the type locality.

Remarks:— Dictyonema duidense is another species in the complex formerly recognized as the single species, Dictyonema sericeum ( Parmasto 1978) . In their treatment of Dictyonema s. str., Lücking et al. (2013a,b) indicated that the phenotype usually identified with the name D. sericeum is a complex of several, phylogenetically distinct species, differing morphologically in the orientation and arrangement of the fibrils and in the morphology of the hymenophore. According to Lücking et al. (2014b) the thallus of D. sericeum type is much more compacted than any of the species collected in South America, indicating, along with the geographic range, that D. sericeum s.str. is a distinct taxon possibly restricted to the Caribean.

Dictyonema duidense is characterized by a shelf-like filamentous thallus, with thick, very broad lobes, areolate, rugose surface and lacking clamp connections. It is very similar to D. barbatum Dal Forno, Bungartz & Lücking ( Dal Forno et al. 2017: 62) from the Galápagos Islands ( Dal Forno 2015, Dal Forno et al. 2017). Both species have a shelflike filamentous thallus and lack clamp connections on the hyphae but D. barbatum is distinguished by the color of the prothallus (old specimens with a darkened hue, yellow to light brown) and the continuous hymenophore. Dictyonema duidense resembles D. excentricum C. Agardh ( Kunth 1822: 1) . This latter is characterized by thick, horizontally arranged bundles of fibrils and is known only from French Guiana.

Additional specimens examined (paratypes):— Amazonas: summit northern Cerro Duida, growing on tree bark in small tepuian forests, elev. 1500 m, March 1996, L. Galiz & V. Marcano AMA-539, 540 (TFAZ, VEN, private herb. V. Marcano).

Figures

FIGURE 7. Dictyonema duidense. A. Habit of the species growing on bark. Photos by V. Marcano.