Leucoagaricus cupresseoides V. Migliozzi & N. Forin sp. nov. Figs. 2–4

MycoBank MB841188.

Etymology:—The epithet ‘ cupresseoides’ refers to its close resemblance to L. cupresseus.

Diagnosis:—The species differs from the other Leucoagaricus species of the section Piloselli in having a vinaceous red pileus with diffracted surface at margins, arachnoid velar remnants on the disc area, predominantly lageniform cheilocystidia, and a unique nrITS sequence.

Holotype: — ITALY. Rome, Castelfusano, in a pine forest near the sea on sandy soil under Pinus pinea, Pinus pinaster and Quercus ilex, 29 November 2014; V. Migliozzi (TR gmb01484). GenBank nrITS accessions from two different basidiomes: OK235667 (TR gmb01484a) and OM327669 (TR gmb01484b).

The description is based on the holotype (Figs. 2–4).

Description:— Pileus medium to large, 80–90 mm diam, convex or plano-convex to applanate depressed in the disc area, without an umbo; disc covered by white arachnoid velar remnants; vinaceous, dark vinaceous red, reddish brown or vinaceous grey, turning bright red after bruising; surface almost smooth, minutely fissured in the pre-marginal area, fragmented at the margin. Lamellae free, white, turning orange-red after bruising, crowded, interspersed with white lamellulae of different lengths; edges entire, concolorous with faces. Stipe 60–80 × 8–12 mm, hollow, cylindrical, white, with a basal bulb up to 15 mm broad, cylindrical, white, turning vinaceous red after bruising, fibrillose. Annulus simple, located at the lower half of the stipe, persistent, ascending, white, particularly adherent to the stipe. Context white. Smell not distinctive, fungoid. Pileus, lamellae and stipe turn brown in dried material.

Basidiospores (6.2–) 6.6– 7.2 –7.7 (–8.6) × (4–) 4.2– 4.5 –4.8 (–5.3) μm, Q= (1.3–) 1.5– 1.6 –1.7 (–1.9) [100, 2, 1], hyaline, smooth, with a visible hilar appendage, without a germ-pore, thin-walled, subglobose to ellipsoid, amygdaliform in side-view, dextrinoid, metachromatic in Cresyl Blue. Basidia 20–28 × 7–8.5 μm, four-spored, clavate; sterigmata 3–4 μm long. Cheilocystidia 30–60 × 10–16 (18) µm, abundant, lageniform to clavate, not pedicellate; with brownish necropigments in dried specimens treated with ammonia. Pleurocystidia not observed. Pileus covering trichodermal, consisting of long and thin-walled hyaline hyphae; terminal elements cylindrical with rounded apex, (80) 100–240 (280) × (8) 9–15 (16) μm, emerging from a tangle of long and thin hyphae (2–4 μm diam); pigment brown both parietal and intracellular, sometimes presence of necropigments in dried specimens with ammonia. Clamp connections absent.

Macrochemical reactions: — Lamellae, pileus and stipe surface becoming dirty green when treated with NH 4 OH.

Habitat and distribution:—Terrestrial, on sandy soil under Pinus pinea, P. pinaster and Quercus ilex. At present known only from the type collection found at Castelfusano (Rome), Italy.

Discussion:—Considering the morphology and the phylogenetic placement (Fig. 1) Leucoagaricus cupresseoides appears close to L. cupresseus, L. aurantiovergens and L. pseudopilatianus. In the phylogram (Fig. 1), L. cupresseoides appears as sister to an unsupported clade consisting of L. aurantiovergens and L. cupresseus, and it falls within a clade (MLB= 83%, BPP= 1) that also includes L. pseudopilatianus (the L. cupresseus complex). The BLASTn results suggested that the closest species to L. cupresseoides was L. cupresseus, with an nrITS sequence identity of 96.6% between OK235667 and AY243630. L. cupresseoides has basidiospores shorter than those reported by Vellinga (2010) for L. cupresseus (6.1–9.3 × 3.9–5.4 μm) and those of L. aurantiovergens and L. pseudopilatianus. Another morphological difference is the presence of velar remnants on the pileus surface of L. cupresseoides not observed in the other three species. Similar lageniform-utriform cheilocystidia are present in L. cupresseus (Vellinga 2010), lageniform cheilocystidia are rare in L. aurantiovergens and not present in L. pseudopilatianus. Arachnoid velar patches on the pileus have been described also in Leucoagaricus gaillardii Bon & Boiffard (1974: 295); nevertheless, the spores of L. gaillardii are longer and wider ((7–) 7.5–11 (–12) × 5.5–6 μm) than those of L. cupresseoides (Gennari et al. 1995; Priou et al. 1995). Moreover, L. gaillardii is not closely related to L. cupresseoides (Fig. 1). A comparative table (Tab. 1) including the distinctive characters among the species of the L. cupresseus complex is provided.