Dictyonema aeruginosulum Lücking, Nelsen & Will-Wolf, 2013

Lücking, Robert, Dal-Forno, Manuela, Lawrey, James D., Bungartz, Frank, Holgado Rojas, María E., Hernández, Jesús E., Marcelli, Marcelo P., Moncada, Bibiana, Morales, Eduardo A., Nelsen, Matthew P., Paz, Elias, Salcedo, Luis, Spielmann, Adriano A., Wilk, Karina, Will-Wolf, Susan & Yánez-Ayabaca, Alba, 2013, Ten new species of lichenized Basidiomycota in the genera Dictyonema and Cora (Agaricales: Hygrophoraceae), with a key to all accepted genera and species in the Dictyonema clade, Phytotaxa 139 (1), pp. 1-38 : 20-22

Dictyonema aeruginosulum Lücking, Nelsen & Will-Wolf , sp. nov. ( Fig. 10 )

Mycobank #805384

Genbank ITS barcoding sequence: EU825955

Differing from the morphologically similar Dictyonema phyllophilum and D. schenckianum in the abundant, coarse, irregular, finger-like projections formed by the vegetative thallus, and from D. irpicinum in the appressedfilamentous growth habit and the lack of clamp connections.

Holotype: — COSTA RICA. Alajuela: Volcán Tenorio National Park, Pilón Biological Station, Arenal- Tempisque Conservation Area , Tilarán Ridge , 140 km NW of San José, 25 km NNW of Tilarán, near Bijagua , access road to station and river; 84° 59' W, 10° 43' N, 700 m; lower montane cloud forest zone, exposed trees and fence posts along pasture, on bark (lower stem), exposed; 16 March 2004, Nelsen 3754 ( INB; isotypes: F, WIS).

Thallus epiphytic on tree trunks, appressed filamentous, covering large areas of the substrate, forming a compressed mat of irregularly arranged to more or less horizontal, densely interwoven, dark aeruginous fibrils resting on a white, byssoid hypothallus; thallus densely furnished with irregular, finger-like projections laterally covered with fibrils, the projections appearing stiff but softening when moistened, becoming branched and confluent, up to 10 mm high and 2 mm broad. Thallus in section 300–800 µm thick (excluding the projections), composed of an upper photobiont layer 200–400 µm thick and a lower medulla (forming the hypothallus) 100–400 µm thick; photobiont layer composed of numerous cyanobacterial filaments wrapped in a closed hyphal sheath formed by jigsaw puzzle-shaped cells, connected to loose hyphae towards the medulla; medulla composed of a loose network of interwoven hyphae sparsely intermingled with cyanobacterial filaments; cyanobacterial filaments composed of 8–12 µm wide and 4–5 µm high, blue-green cells penetrated by tubular fungal hyphae; heterocytes sparse, pale yellow, 7–11 µm wide and 3–4 µm high; cells of hyphal sheath wavy in lateral outline, 3–4 µm thick; medullary hyphae and those associated with hyphal sheath straight, 4–6 µm thick, lacking clamp connections. Projections in section formed by a network of medullary hyphae 4–6 µm thick, lacking clamp connections, loosely intermingled with cyanobacterial filaments internally and with a denser layer of filaments formed on the outside except the apical regions.

Hymenophore developed as irregular, resupinate patches on the thallus surface or on the underside of the projections and then soon becoming inverted and exposed, with pale yellow, smooth surface; hymenophore in section 50–100 µm thick, composed of a paraplectenchymatous layer resting on loose medullary hyphae and supporting the hymenium; hymenium composed of numerous, palisade-like basidioles and scattered basidia; basidioles 10–20 × 5–7 µm; basidia 15–25 × 5–8 µm, 4-sterigmate; basidiospores (few seen) ellipsoid to narrowly drop-shaped, non-septate, hyaline, 7–9 × 3–4 µm.

Chemistry: no substances detected by TLC.

Distribution and Ecology: —This species is thus far known from montane rain forest in the northern Cordillera de Tilarán in Costa Rica, forming extensive mats on the trunks of semi-exposed trees of Syzygium jambos in a pasture along the road in an area with abundant precipitation. Unfortunately, a few years after collecting the material, the trees in this spot were completely logged, so the holotype population is likely extirpated.

Etymology: —The epithet refers to the characteristic blue-green color of this species, while most other species are either more bluish or greenish.

Remarks: — Dictyonema aeruginosulum is one of several species now segregated from D. sericeum , disentangling the broad concept of that species laid out by Parmasto (1978). While that author focused on mycological features of the basidiomata and regarded variation in thallus morphology as of no taxonomic value, molecular phylogenetic data clearly show that D. sericeum sensu Parmasto contains a large number of different species and even the shelf-like forms representing D. sericeum in a narrow sense are more than one species ( Dal-Forno et al. 2013). Due to the distinct white hypothallus formed by a well-developed, laterally projecting medullary layer, D. aeruginosulum is most similar to D. phyllophilum (Parmasto) Lücking , Dal- Forno & Lawrey, comb. et stat. nov. [Mycobank #805390; bas.: D. sericeum f. phyllophilum Parmasto , Nova Hedwigia 29: 113 (1978); holotype: Malaysia (Borneo: Sarawak), Beccari 222 (B; isotype: W!)]. It differs from the latter chiefly in the conspicuous finger-like projections. Also, all known collections of D. phyllophilum are sterile. Phylogenetically, the two species do not appear to be closely related. Finger-like projections, though smaller, are also known from D. scabridum (Vain.) Lücking , comb. et stat. nov. [Mycobank #805391; bas.: Rhipidonema irpicinum f. scabridum Vain., Ann. Acad. Sci. Fenn., Ser. A , 19(15): 29 (1923); syn.: Dictyonema ligulatum f. scabridum (Vain.) Parmasto , Nova Hedwigia 29: 120 (1978); lectotype ( Parmasto 1978: 120): Philippines, Weber 1391 (TUR-Vainio 32883!; isotype: W!)] and from D. irpicinum Mont. ( Montagne 1848: 119; holotype in PC checked), which both differ in the shelf-like growth and the presence of clamp connections, and D. scabridum also in the densely arranged fibrils forming an almost compact surface ( Parmasto 1978).

Additional specimens examined: — COSTA RICA. Alajuela: Volcán Tenorio National Park, Pilón Biological Station, Arenal-Tempisque Conservation Area , Tilarán Ridge , 140 km NW of San José, 25 km NNW of Tilarán, near Bijagua , access road to station and river; 84° 59' W, 10° 43' N, 700 m; lower montane cloud forest zone, exposed trees and fence posts along pasture, on bark (lower stem), exposed; 15 March 2004, Will-Wolf 12733 ( F, INB, USJ, WIS) .

Figures

FIGURE 10. Dictyonema aeruginosulum (holotype). A. Thallus with projections. B. Thallus surface enlarged showing filaments. C. Hymenophore. Scale = 1 mm.