17. Volvariella deceptiva Consiglio & Ševčíková sp. nov. (Fig. 25).

MycoBank: MB 856534

Typification:— Holotype. ITALY. L’Aquila: Opi, Val Fondillo, in a grassy area, at the edge of a mixed forest with Fagus sylvatica and Abies alba, 22 September 2005, G. Consiglio & M. Contu, AMB19290!

Etymology—From the Latin “ deceptiva ”, misleading, deceptive, because this species was initially confused with Volvariella pusilla.

Diagnosis:— Volvariella deceptiva is characterized by the small, white to pale grey basidiomes, and it can only be reliably distinguished from morphologically similar taxa by its nrITS sequences, which differs in 9 changes from its closest relative (V. graminicola).

Description:— Pileus 10–45 mm diam., convex or hemispherical when young, expanding to conico-convex then plano-convex, sometimes becoming umbilicate or concave; surface smooth or slightly to distinctly radially fibrillose, not hygrophanous, white or grey overall, some with grey or ochre centre, paler towards the margin; margin striate or not, slightly exceeding the lamellae and irregular. Lamellae crowded, free, broadly ventricose, white when young, becoming salmon pink or fleshy pink to pinkish brown with age; edge entire, or irregular, concolourous. Stipe 10–60 × 5–9 mm, cylindrical, slightly widening towards the base, straight or slightly curved; surface white, smooth to finely fibrillose or pubescent. Volva membranaceous, saccate, in some basidiomes with slightly nodulose surface, white to grey-brown, with 2–4 lobes. Context white with indistinct or fungoid smell.

Basidiospores (n=120, c=2) (5.0–)6.3–7.1(–9.0) × (3.9–)4.6–5.4(–6.1) μm, avl × avw = 6.2 × 4.6 μm, Q = 1.22– 1.49, avQ = 1.35, broadly ellipsoid to ellipsoid, with an amygdaliform outline, less frequently ovoid, thick-walled, with distinct hilar appendage up to 0.3–0.6 μm long. Basidia 21–30 × 6–10 μm, tetrasterigmate, (narrowly) clavate. Lamella edge heterogeneous or completely covered with cystidia. Cheilocystidia common (40–)44–97 × (13–)14–36 μm, pyriform, utriform, (broadly) fusiform, (broadly) clavate or broadly lageniform, sometimes with a small apical papilla. Pleurocystidia scarce, 41–67 × 12–30 µm, similar to cheilocystidia, in some collections predominantly utriform. Pileipellis a cutis or an intermediate cutis-trichoderm, with terminal elements 5–25 μm wide, some slightly gelatinized, often constricted at the septa, with hyaline contents. Stipitipellis a cutis, or a cutis-trichoderm in the upper part of the stipe, with cylindrical hyphae 6–15 μm wide. Volva composed of interwoven, cylindrical hyphae, 5–34 μm wide, constricted at the common septa. Clamp connections absent in all parts examined.

Habit, habitat, and phenology:—Solitary of gregarious, terrestrial. On grassy areas at the edge of forests, in steppes, or in parks. September–October.

Distribution:—Europe (Czech Republic France, and Italy).

Additional collections examined:— CZECH REPUBLIC. Moravia: Biskoupky na Moravě, near path from Biskoupská hadcová step Nature reserve to Jihlava river, in the meadow, serpentine subsoil, 21 October 2017, H. Ševčíková & P. Ševčík, BRNM 804994. FRANCE. Alpes-Maritimes: Nice, Parc de Vaugrenier, among grass, 15 October 2007, S. Kelly, K (M)156178.

Observations:— Volvariella deceptiva is characterized by the small, white to pale grey basidiomes.Phylogenetically it belongs in the same clade as V. graminicola, V. pusilla, and two likely undescribed species (OP114059 and PP660764). All these taxa are very similar morphologically, but there are clear and constant differences between the nrITS sequences of these species: nine differences between V. deceptiva and V. graminicola and 17 differences between V. deceptiva and V. pusilla.

Volvariella sp. (PP660764) differs by its more ellipsoid spores and shorter cheilocystidia, but these characters need verification because only one collection was found so far. The only known collection of this species (JB14/654) has been studied by us, and included in the phylogeny, but it is not formally described here.

Morphologically similar species include V. pusilla, V. neoparvula, V. globifera, V. latispora, V. pilosipilea and V. reidii. See Tables 1 and 2 for a detailed comparison.