Caballero, Justo & L.A. Parra, 2025

Caballero, Fernando, Justo, Alfredo, Parra, Luis A., Angelini, Claudio, Consiglio, Giovanni, Dovana, Francesco, Ferisin, Giuliano, Kaygusuz, Oğuzhan, Knudsen, Henning, Llimona, Xavier, Muñoz, Guillermo, Daniëls, Pablo P., Pérez-De-Gregorio, Miquel À., Ševčíková, Hana, Valverde, Andrés & Vizzini, Alfredo, 2025, Taxonomic and phylogenetic overview of the genus Volvariella (Volvariellaceae), with a focus on European species, Phytotaxa 680 (1), pp. 1-85 : 74-76

27. Volvariella siquieri F. Caballero, Justo & L.A. Parra , sp. nov. ( Fig. 35 ).

MycoBank: MB 856544

Typification:— Holotype: SPAIN. Balearic Islands: Mallorca, Santanyí , Parc Natural de Mondragó , on plant matter, in coastal dune under Pinus halepensis , 8 November 2001, J. L. Siquier, AH602551 ! (Isotype: JLS 1232 ).

Etymology:—Honouring the collector of the holotype, Spanish mycologist and friend José Leonardo Siquier as a sign of gratitude for his contributions to mycology.

Diagnosis:— Volvariella siquieri is characterized by its medium size, and the dark-grey colours when young, becoming paler over time, staying dark only at pileus centre, and the thick, grey volva.

Description:— Pileus 20–40 mm diam., convex when young, expanding to plano-convex or slightly depressed at centre, with a low, broad umbo; surface radially fibrillose, sometimes grouped in small squamules, not hygrophanous, grey overall, with darker, almost black centre; margin smooth or slightly striate, slightly exceeding the lamellae and irregular. Lamellae crowded, free, broadly ventricose, white when young, becoming salmon pink or pinkish brown with age; edge entire, or irregular, concolourous. Stipe 30–40 × 4–9 mm, cylindrical, slightly widening towards base, straight or slightly curved; surface white, smooth to finely fibrillose. Volva membranaceous, thick, saccate, white, brown to grey-brown, with two lobes; rhizomorphs not observed. Context white with indistinct smell.

Basidiospores (n=87, c=1) 5.3–8.0 × 4.6–7.0 μm, avl × avw = 6.6 × 5.6 μm, Q = 1.00–1.41, avQ = 1.19, globose to ellipsoid, thick-walled, with barely distinct hilar appendage. Basidia (22–)29–35(–45) × 9–11 μm, bisterigmate, monosterigmate and tetrasterigmate, clavate, subclavate or subcylindrical. Lamella edge heterogeneous or sterile. Cheilocystidia common, (38–)45–64(–76) × (11–)17–22(–26) μm, (broadly) fusiform, lageniform, utriform or clavate. Pleurocystidia scarce, 40–73 × 12–19 µm, similar to cheilocystidia. Pileipellis a cutis or an intermediate cutis-trichoderm, with terminal elements (9–)12–23(–29) μm wide, often constricted at the septa, hyaline or with pale olive brown pigment. Stipitipellis a cutis or a cutis-trichoderm in upper part of stipe, with cylindrical hyphae 4–30 μm wide. Volva composed of interwoven, cylindrical hyphae, 2–21 μm wide, with common septa, on the external surface often gelatinized. Clamp connections absent in all parts examined.

Habit, habitat, and phenology:—Gregarious. Terrestrial, among plant debris, in coastal dunes under Pinus halepensis . November.

Distribution:— Spain (Balearic Islands: Mallorca).

Observations:—Compared to Volvariella siquieri , V. sylvipraticola has larger basidiomes (pileus up to 60 mm diam.), larger cystidia, up to 90 µm long; and rhizomorphs with clamped hyphae. Volvariella dunensis differs in the larger basidiomes (pileus 28–100 mm diam.), larger basidiospores (7.3 × 5.2 µm on average), and presence of caulocystidia. Volvariella taylorii differs in the larger cheilocystidia (up to 122 µm long), narrower basidiospores (4.7 µm wide on average) with higher Q values (1.17–1.93, avQ= 1.50). Volvariella murinella differs in the larger basidiomes (pileus 20–70 mm diam.), and larger cheilocystidia, up to 120 µm long. Volvariella caesiotincta also has larger basidiomes with pileus 25–70 (–120) mm diam., pileipellis hyphae with very dark olive brown pigment (especially in the suprapellis), and rhizomorphs with clamped hyphae.

Figures

FIGURE 35. Volvariella siquieri (AH602551, holotype). A. Basidiomes; B–H. Microscopic characters. B–C. Cheilocystidia; D. Pleurocystidia; E. Spores; F–G. Pileipellis; H. Volva hyphae. Bar: (B–H) = 10 µm. Photos by J.L. Siquier (A), F. Caballero (B–H).