Dictyonema umbricola V. Marcano 2022, sp. nov.
Creators: name: Marcano, Vicente
Publisher: name: Zenodo
Year: 2022
Subjects: Biodiversity
Taxonomy
Fungi
Basidiomycota
Agaricomycetes
Agaricales
Hygrophoraceae
Dictyonema
Dictyonema umbricola

description: 8) Dictyonema umbricola V. Marcano, sp. nov.; (Fig. 11)
Mycobank MB#838498
Diagnosis:— Sicut Dictyonema discocarpum, sed filamentis furcatis, marginibus albidis, et hyphis fibulatis differt. Thallus muscicola. Hyphothallus praesentia. Hymenocarpus elevatus, disciformibus, margine tomentoso. Hymenium N non reagens. Basidiosporae obovatae, 9–10 μm longae, 4–5 μm crassae.
Type:— VENEZUELA. Mérida: Parque Sierra Nevada de Mérida, Raiz de Agua cloud forests, elev. 2550 m; 15 June 2020, V. Marcano & L. Castillo 20-91 (holotype MER, isotype B, private herb. V. Marcano).
Etymology:—The epithet refers to the very shady habitat.
Description:— Thallus growing on bryophytes, filamentous, dark blue-green, covering shorter areas of the substrate, by irregular, discontinuous patches up to 12 cm across, composed of loosely interwoven, dark green to bluish green fibrils leaving interspaces and bordered by a distinct, discontinuous, white margin (prothallus). Fibrils subascending or horizontal, with whitish apices, broad, more loosely and irregularly arranged and leaving interspaces. Thallus (when fresh) in section 1.25–2.5 mm thick, composed of a thick, loose, photobiont (Rhizonema) layer (0.75–1.75 mm) and a pale brown medulla (0.5–0.75 mm) (hypothallus); photobiont layer composed of cyanobacterial filaments covered by thin elongated fungal cells, forming jigsaw-puzzle-shaped cells; cyanobacterial filaments branched, composed of 13–17 μm wide and 7–10 μm high, bluish green cells, cylindrical, in chains, penetrated by tubular fungal hyphae (haustoria); heterocytes frequent, pale to slightly bright yellow, 12–13 μm wide and 2–3 μm high, narrowly elliptic; cells of hyphal sheath variably wavy in lateral outline, 2–3 μm thick; hyphae of hypothallus straight, branched, hyaline, smooth, 3–5 μm thick. Clamp connections present on the hyphae, abundant.
Hymenophore (when fresh) developed as small, rounded to irregular, corticioid patches, dispersed on the upper surface of thallus and resembling apothecial discs, 0.6–2 mm diam., with pale yellowish, smooth surface and white, minutely tomentose margins, 125–200 μm diam.; hymenophore in section 50–120 μm thick, composed of a paraplectenchymatous layer connected to loose medullary hyphae, 5–6 μm wide; hymenium composed of numerous, palisade-like basidioles and scattered basidia; basidiospores (only a few seen) obovate, non-septate, hyaline, 9–10 × 4–5 μm.
Chemistry:—Thallus K–, C–, KC–, P–; medulla K–, C–, KC–, P–, N–, ER–; basidiocarp K–, C–, KC–, P–, N–, ER– (n = 8). No lichen compounds detected by TLC.
Distribution and Ecology:—This species is known only from the well-developed type collection. It was found growing on mosses in a very shady and humid rainforest at elev. 2000–2650 m (Fig. 9A).
Remarks:— Dictyonema umbricola is characterized by horizontal or subascending fibrils, branched cyanobacterial filaments, jigsaw-puzzle-shaped cells, abundant clamp connections on the hyphae and a negative N spot test.This species resembles D. discocarpum Lücking, Dal Forno & Wilk (Lücking et al. 2013b: 7). Both species have a hymenophore composed of disc-shaped patches resembling apothecial discs, with pale yellowish, smooth surface, minutely tomentose margins and jigsaw-puzzle-shaped cells. However, the latter has shelf-like filamentous thallus, a hymenophore in smaller disc-shaped patches (0.3–0.5 mm diam.) dispersed on the underside of the thallus, a hypothallus with byssoid margin, and lacks clamp connections. Dictyonema discocarpum is known only from Bolivia (Lücking et al. 2013b).
Some species of the genus Cyphellostereum (Lawrey et al. 2009) have disc-like hymenophores forming resupinate, rounded patches, viz., C. jamesianum Dal Forno & Kaminsky (Dal Forno et al. 2019: 338), and C. georgianum Dal Forno, McMullin & Lücking (Dal Forno et al. 2019: 337). Yet, these species are characterized by a crustose, dark green thallus formed by loose individual fibrils, a fungal sheath consisting of irregular, thin, branched hyphae surrounding the cells, and absence of jigsaw-puzzle-shaped cells. Both species are known only from the southeastern United States and Puerto Rico.
Additional specimens examined (paratypes):— Mérida: Parque Sierra Nevada de Mérida, Raiz de Agua, cloud forests, elev. 2650 m; 12 October 2020, V. Marcano & L. Castillo 20-577 (MER, private herb. V. Marcano); Parque Sierra Nevada de Mérida, road towards Lake Coromoto, cloud forest, elev. 2000 m, V. Marcano & L. Castillo 21-110 (MER, private herb. V. Marcano).
description: Published as part of Marcano, Vicente, 2022, Eight new species of lichenized Basidiomycota in the genera Acantholichen, Cyphellostereum and Dictyonema s. str. (Agaricales, Hygrophoraceae) from northern South America, pp. 199-225 in Phytotaxa 574 (3) on pages 218-220, DOI: 10.11646/phytotaxa.574.3.1, http://zenodo.org/record/7380966