Mycena eucalypticola Traba, Couceiro & M.Villarreal sp. nov.

MycoBank: MB 841234

Figs 10–12, 19

Diagnosis

Mycena eucalypticola sp. nov. is distinguished from M. globispora, which has similar cherocytes, by its ellipsoid basidiospores and caulocystidia lacking long outgrowths in the middle.

Etymology

Referring to the substratum where the new species was first found.

Type material

Holotype SPAIN • A Coruña, Oza-Cesuras, Santiago de Reboredo; 43°13′46ʺ N, 8°10′15ʺ W; 122 m a.s.l.; 16 May 2021; A. Couceiro s.n.; on dead leaves of Eucalyptus globulus; GenBank no.: MZ393494 (ITS, partial sequence, not used in the molecular analyses), OQ427382 (ITS); AH [AH56005].

Additional material examined

SPAIN • A Coruña, Paderne, San Salvador de Velouzás, Condós; 43°18′46ʺ N, 8°09′24ʺ W; 122 m a.s.l.; 15 Jan. 2022; A. Couceiro, J.M. Traba, A. Vila & M. Villarreal s.n.; on dead leaves of Eucalyptus globulus; AH [AH56023] • A Coruña, Ortigueira, Playa de Morouzos; 43°41′55ʺ N, 7°50′49ʺ W; 7 m a.s.l.; 8 Dec. 2022; A. Couceiro, A. Jurado, C. Sos & M. Villarreal s.n.; on falling bark of Laurus nobilis; AH [AH57608] • Fragas do Eume, Pontedeume; 43°40′99ʺ N, 8°8′44ʺ W; 19 m a.s.l.; 3 Nov. 2024; A. Cortés-Pérez, A. Couceiro & M. Villarreal s.n.; on dead leaves of Betula alba and Salix atrocinerea; AH [AH60331] • A Coruña, Ortigueira, Playa de Morouzos; 43°41′54ʺ N, 7°50′48ʺ W; 7 m a.s.l.; 2 Mar. 2022; J. Traba & A. Couceiro s.n.; on leaves of Salix atrocinerea; GenBank no.: OQ427383; PR [PR4020422783].

PORTUGAL • Madeira, Ribeira do Seixal; 32°48′16ʺ N, 17°07′03ʺ W; 570 m a.s.l.; 13 Feb. 2024; A. Couceiro, C. Sos & M. Villarreal s.n.; dead leaves of Laurus novocanariensis; AH [AH60107] • Madeira, Arco de São Jorge; 32°49′24ʺ N, 16°57′13ʺ W; 240 m a.s.l.; 14 Feb. 2024; A. Couceiro, C. Sos & M. Villarreal s.n.; dead leaves of Laurus novocanariensis; GenBank no.: PP865076; AH [AH60108].

Description

Primordia 0.15–0.7 mm diam., hemispherical to paraboloid, covered with white granules, initially forming a closed layer, soon breaking up to a non-contiguous layer upon a white surface. Pileus 1–2 mm diam., initially conical or parabolic, expanding to hemispherical or convex to plano-convex with age; margin straight or slightly crenate, translucent-striated; surface delicately pruinose to granular throughout, almost furrowed, pure white. Context white, inconspicuous. Lamellae free, adnate or closely adnate, ascending, distant to subdistant, 5‒8 reaching the stipe, with 0‒1 lamellulae, up to 0.3 mm wide, white, with rectilinear or slightly convex edges, pruinose under lens and concolorous. Stipe 1–17 × 0.15– 0.25 mm, central, filiform or very slightly enlarged towards the base, hollow; surface entirely covered by erect white hairs, insititious, white, watery white to almost translucent. Indistinct odour and taste.

Basidiospores (5.6‒)6.4‒8.3(‒9.8) × (3.6‒)3.9‒5(‒5.6) µm; Q = (1.4‒)1.5‒1.8(‒2); n = 100; Me = 7.3 × 4.4 µm; Qe = 1.7, elongate to cylindric, smooth, hyaline, amyloid, thin-walled, indistinctly guttulate. Basidia 9–17.5 × 7–9 μm, obovoid to broadly clavate, 2- or 4-spored, sterigmata up to 5 μm long., not clamped at the base. Cheilocystidia 15.5‒22.6(‒35.9) × 9.2‒14.8 μm, ellipsoid, obovoid, clavate to fusoid or subcylindrical, covered densely with outgrowths, hyaline, thin-walled; outgrowths 0.5–1.6(‒3) × 0.5–1 μm, cylindrical, mixed with the basidia. Pleurocystidia absent. Pileipellis a cutis covered by a universal veil composed of acanthocysts and cherocytes; hyphae 2–17 μm diam., smooth or covered by short outgrowths 0.5–2.5 × 0.5–1 μm, hyaline, with terminal acanthocysts 8.5–36(‒47.5) × 8–25 μm, claviform or broadly claviform to subglobose or ovoid, covered densely with outgrowths, hyaline, thin-walled; outgrowths 0.5–2.5(‒4.5) × 0.5–1 μm, cylindrical, apex obtuse. Acanthocysts abundant, sometimes detached, 15–32 × 9–19 μm, globose, obpyriform, vesiculose, sphaeropedunculate, entirely densely spinulose, hyaline to pale greyish in KOH or water, dextrinoid, thin-walled; spinulae up to 1.5 μm × 1 μm at base, bluntly conic, obtuse. Cherocytes 12.5–21.5 × 9–16 μm, ellipsoid, broadly clavate to obovoid, hyaline, thick-walled (up to 3 μm), covered with outgrowths, 0.5–4 × 0.5–3 μm, solid or thick-walled, crystalline-like rounded. Hypodermium, hyphae 3–25 μm diam., hyaline, dextrinoid. Lamellar trama regular to subregular; hyphae 2–21 μm diam., hyaline, dextrinoid. Cortical and medullary hyphae of the stipe 1–7.5 μm diam., with terminal or lateral caulocystidia. Caulocystidia 45–168 × 4–9(‒11.5) μm, short to broadly clavate or subcylindrical to long and cylindrical, usually with subcapitate at apex, densely spinulose; hyaline, thin-walled; spinulae 0.5–5 × 0.5–1.25 μm, cylindrical or subconical. Clamp connections are present but hard to find.

Habitat and distribution

Growing gregarious on dead leaves of Betula, Eucalyptus, Laurus, and Salix. Known from Spain and Portugal (Fig. 19).

Remarks

M. eucalypticola sp. nov. is a predominantly foliicolous species that has been found fruiting on dead leaves of Betula alba, Eucalyptus globulus, Salix atrocinerea, and Laurus novocanariensis in four different localities of Galicia and Madeira. Only one collection has been found fruiting on decaying bark of Laurus. Macroscopically, it could be mistaken for a small species of Hemimycena Singer because of its absence of a basal disc and the diminutive white basidiomata featuring scant lamellae. However, it possesses amyloid spores and microcharacters that are very different from those of Hemimycena s. lat. Microscopically, it is characterised by its singular cherocytes provided with large globose crystalline-like excrescences and ornamented caulocystidia frequently subcapitated. Only M. globispora (= M. alphitophora var. globispora Manim. & Leelavathy) described from India (Aravindakshan & Manimohan 2015) shows a universal veil composed of similar cherocytes that are thick-walled and with broader excrescences towards the apex, and that are present both over the pileus and at the stipe base. However, this species differs from M. eucalypticola in having globose to subglobose basidiospores, and longer cylindrical caulocystidia with longest excrescences at the middle region. Unfortunately, there is no sequence for M. globispora to determine its phylogenetic proximity to M. eucalypticola.

M. eucalypticola sp. nov. should not be confused with M. eucalipticola Losa, which is a nomen nudum (Maas Geesteranus 1983b).