Dictyonema laurae 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 : 213-215

5) Dictyonema laurae V. Marcano , sp. nov.; ( Fig. 8 ) Mycobank MB#840644

Diagnosis:— Sicut D. subsericeum , sed hyphis non fibulatis differt. Thallus muscicola , byssaceus, tenuis, marginibus elevatis, pagina hirsuta. Hymenocarpus resupinatus. Hymenium N reagens (roseus). Sporis elliptis, hyalinis, non septatis, 10–12 μm longis, 7–8 μm latis.

Type:— VENEZUELA. Mérida: Parque Sierra Nevada de Mérida, Raiz de Agua cloud forests, elev. 2650 m, 17 July 2021, V. Marcano 21-65 (holotype MER, isotype B, private herb. V. Marcano) .

Etymology:—The epithet is dedicated to the naturalist Laura Castillo who has contributed with the author to the study of lichens and in discovering new species.

Description:— Thallus on liverworts or mosses, byssaceous, filamentous, forming a thin crust, epiphytic on tree branches. Thallus surface irregular, more or less continuous, covering up to 12 cm across, greenish blue, developing a mat of cyanobacterial fibrils leaving interspaces, bordered by a discontinuous, fibrillose, narrow, white margin projecting vertical from the substrate, 2–4 mm broad; surface hirsute. Thallus (when fresh) in section 1.75–2 mm thick, composed of a loose, white medulla (0.75–1 mm) (hypothallus) and a broad, very loose aeruginous upper layer (1–1.25 mm) composed of irregularly arranged, long, white fibrils mixed with photobiont filaments ( Rhizonema ); cyanobacterial filaments wrapped in a closed hyphal sheath formed by jigsaw puzzle-shaped cells; cyanobacterial filaments not divided, composed of 12–17 μm wide and 7–8 μm high, bluish green cells penetrated by tubular fungal hyphae (haustoria); heterocytes frequent, bright yellow, elliptic, 10–12 μm wide and 5–8 μm high; hyphae associated with hyphal sheath straight, hyaline, 5–7 μm thick, smooth towards the tips of the filaments; clamp connections absent; hyphal sheath waxy in lateral outline.

Hymenophore (when fresh) developed as small, angular to elongate, white, resupinate patches dispersed on the underside and resembling small, isomorphic attachment, small hapters (250–300 × 300–500 μm) with white, finely reticulate surface and entire margins; hymenophore composed of a paraplectenchymatous layer connected to loose medullary hyphae, 6.25–7.5 μm wide; hymenium composed of numerous, palisade-like basidioles and scattered basidia; basidia 32–39 × 5–7 μm, 4-sterigmate; basidiospores elliptic, non-septate, hyaline, 10–12 × 7–8 μm.

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

Distribution and Ecology:— Dictyonema laurae was found growing as an epiphyte on bryophytes in the canopy of partly shady and very humid rainforests at elev. 2450–2650 m ( Fig. 8A ). It is associated with Grammitis , Cladonia and Parmotrema species.

Remarks:— Dictyonema laurae is characterized by a thallus forming a thin crust (1.75–2 mm), with an irregular, continuous, greenish blue, hirsute surface, with discontinuous, fibrillose, narrow margins ascending from the substrate, hapteriform hymenophore patches with finely reticulate surface and entire margins, absence of clamp connections on the hyphae, large basidiospores, and a positive N spot test (pink). Dictyonema laurae is similar to D. subsericeum ; which occupies the same habitat and has hymenophores resembling attachment hapters. However, D. subsericeum has a thallus forming a thicker crust (3–5 mm), with filamentous lobes, semicircular or hemispherical, projecting horizontally from the substrate, is variable in color (white, greenish blue, brown), size and shape (semicircular and hemispherical), with clamp connections on the hyphae, wider cyanobacterial cells, with a larger, irregular hapteriform hymenophore with more or less smooth or pruinose surface and fibrillose margins, smaller basidiospores, and a negative N spot test.

Dictyonema laurae is also like D. hapteriferum Lücking, Dal Forno & Wilk ( Lücking et al. 2013b: 11) and D. subinvolutum . However, D. hapteriferum is characterized by an absence of clamp connections, cyanobacterial filaments composed of 10–12 μm wide cells, a hymenophore resembling large attachment hapters but has semicircular, shelf-like, filamentous lobes and hymenophore with beige surface; it is known only from Bolivia and Perú. Dictyonema subinvolutum has a thallus developing a mat of interwoven fungal-cyanobacterial fibrils, leaving interspaces connected by a defined hypothallus; the cyanobacterial filaments are 12–15 μm wide, have clamp connections, and the basidiocarp surface is pruinose with slightly involute margins. Both species D. laurae and D. subinvolutum show a positive N spot test (pink).

Additional specimens examined (paratypes):— Mérida: Parque Sierra Nevada de Mérida, Raiz de Agua cloud forests, elev. 2450 m, 17 July 2021, V. Marcano 21-78, 21-79 (MER, private herb. V. Marcano).

Figures

FIGURE 8. Dictyonema laurae. A. Habit of the species growing on bryophytes, scale = 2.5 cm. B. Thalli showing irregular, ascendant to erect fibrils, scale = 1 cm. C. Close up showing hymenophore developed on the underside, scale = 0.4 cm. D. Details on aeruginous fibrils of the thallus upper layer, scale = 0.2 cm. Photos by V. Marcano.