Acantholichen dendroideus 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 : 207-208

1) Acantholichen dendroideus V. Marcano , sp. nov.; ( Fig. 4 )

Mycobank MB#838340

Diagnosis:— Sicut Acantholichen campestris , sed squamis dense dichotome furcatis differt. Thallus muscicola , microsquamulosus. Squamulae microfruticosae, pruinosae. Soredia nulla. Hyphis tegentibus fibrillas quadratorhombicis, non fibulatis. Acanthohyphidiae 20–27 longae × 5–7 μm crassae, subglobosae vel pyriformae, conspicue spinosae, abundantes.

Etymology:—The epithet refers to the characteristic squamules which are divided at the top fine ramifications.

Type:— VENEZUELA. Mérida: Parque Sierra Nevada de Mérida, La Mucuy Alta , elev. 2150 m; 5 November 2020, V. Marcano 20-901 (holotype MER, isotype B, private herb. V. Marcano) .

Description:— Thallus microsquamulose; squamules thin and mostly elongated, 1–2 mm long, 100–180 μm broad, microfruticulose, many growing together, occasionally thus shading one another, olivaceous when fresh, light blue grey when dry, the shaded parts becoming necrotic and pale beige, attached basally to the substrate, densely and dichotomously divided from the tips; microbranches swollen, 1–3(–4) times divided, coral-like, ascendent or erect, 300–350 μm long, 40–60 μm broad. An overall uniformly white-pruinose appearance due to acanthohyphidia. Soredia absent. Thallus in cross section 60–110 μm thick, composed of a thick photobiont ( Rhizonema ) layer (60–80 μm), a very thin paraplectenchymatous cortex and pale brown medulla. Photobiont forming clusters of coiled cyanobacterial filaments (chroococcoid; 7–14 μm diam.) inside the thallus microsquamulose, wrapped in a dense hyphal sheath formed by jigsaw-puzzle-shaped cells. Acanthohyphidia variable in size, usually small (4–8 μm × 4–5 μm), irregular, subglobose to pyriform, sometimes large [20–24(–27) × 5–7 μm] and then elongate, apically thickened, conspicuously spiny, abundant, present on upper and lower surfaces. Clamp connections not observed.

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

Distribution and Ecology:—This species is known only from the well-developed type collection. It was found on mosses in a humid, shady disturbed forest growing on Persea americana P. Miller (1768 : HW’95) associated with Cora , Pseudoparmelia Lynge (1914: 15) and Usnea species at 2100–2550 m ( Fig. 3A ).

Remarks:—The genus Acantholichen , previously thought to be monospecific ( Lawrey et al. 2009), currently includes six species, viz., A. sorediatus Dal Forno, Sipman & Lücking (2016: 49) and A. pannarioides from Costa Rica (this latter also from Venezuela) ( Jørgensen 1998), A. albomarginatus Dal Forno, Marcelli & Lücking (2016: 43) and A. campestris Dal Forno, Spielmann & Lücking (2016: 44) from Brazil, A. galapagoensis Dal Forno, Bungartz & Lücking (2016: 44) from the Galápagos islands, and A. variabilis Dal Forno, Coca & Lücking (2016: 51) from Colombia ( Dal Forno 2015, Dal Forno et al. 2016, 2017).

Acantholichen dendroideus is morphologically distinct from all other known Acantholichen species. It is characterized by a light blue-grey (when dry) thallus, ascendent, dichotomously and densely branched (from the tips) microsquamules, a pruinose surface and large acanthohyphidia. The new species somewhat resembles A. campestris from Brazil and A. galapagoensis from the Galápagos islands. Both species lack soredia and have a branched thallus and pyriform acanthohyphidia. However, in A. campestris the squamules are not dichotomously branched, are grey (when dry), and show a microfruticulose appearance while growing into vertical structures; the acanthohyphidia are small (10–15 × 6–8 μm). It is the only species known that grows on rocks. In contrast A. galapagoensis has dark olivaceous grey (when dry), elongated, intricate and tiled squamules, a non-fruticose appearance, small to medium acanthohyphidia (12–16 × 6–10 μm), and grows on mosses and liverworts ( Dal Forno et al. 2016).

Additional specimens examined (paratype):— Mérida: Parque Sierra Nevada de Mérida, Raiz de Agua, cloud forests, elev. 2550 m; June 2020, V. Marcano & L. Castillo no. 20-416 (MER, private herb. V. Marcano).

Figures

FIGURE 3. Distribution of Dictyonema s.lat. species in Venezuela. 1. Acantholichen dendroideus. 2. Cyphellostereum mucuyense. 3. Dictyonema andinum. 4. D. duidense. 5. D. laurae. 6. D. subinvolutum. 7. D. subsericeum. 8. D. umbricola. A. Andes. B. Cerro Duida.

FIGURE 4. Acantholichen dendroideus. A. Habit of the species growing on mosses. B–C. Thallus showing ascendant, densely and dichotomously branched microsquamules; scale in B = 1 cm, scale in C = 0.5 mm. D–E. Close up showing microfruticose, coral-like squamules; scale in D = 0.1 mm, scale in E = 0.2 mm. Photos by V. Marcano.