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 : 52

15. Volvariella cordispora F. Caballero, Justo & L.A. Parra , sp. nov. ( Fig. 23 ).

MycoBank: MB 856532

Typification:— Holotype: SPAIN. Burgos: Guma, 41.638435, -3.509393, elev. 820 m among ruderal plants ( Eryngium campestre , Plantago sp. ) at the centre of a path between a cereal field and the Duero river, 9 June 2018, L. A. Parra, AH60254! (Isotype: LAP 190).

Etymology:—From the Latin “ cor/cordis ” heart and “ spora ” spore, because of the frequent heart-shaped spores observed in the holotype.

Diagnosis:— Volvariella cordispora is characterized by its robust habit, white pileus with pale brown colours at centre and a striate margin, dark grey saccate volva, presence of frequent heart-shaped spores, and terrestrial ruderal habitat.

Description:— Pileus 30–44 mm diam., convex when young, expanding to plano-convex, with or without a low, broad umbo, sometimes with a patch of universal veil remnant at centre; surface fibrillose or covered with small squamules, not hygrophanous, white overall, with pale brown colours at centre; margin striate, slightly exceeding, and irregular. Lamellae crowded, free, broadly ventricose, white when young, becoming salmon pink or pinkish brown with age; edge entire, or irregular, concolourous. Stipe 20–40 × 5–7 mm, cylindrical, slightly widening towards the base, straight or slightly curved; surface white, smooth to finely fibrillose. Volva membranaceous, saccate, fragile, brown to grey-brown, with 3–4 lobes; rhizomorphs not observed. Context scarce, white; smell not recorded.

Basidiospores (n=70, c=1) 5.0–8.1 × 3.8–5.2 μm, avl × avw = 6.0 × 4.6 μm, Q = 1.10–1.65, avQ = 1.30, subglobose to oblong, frequently with a heart-shaped outline, thick-walled, with barely a hilar appendage. Basidia 16–36 × 7–10 μm, tetrasterigmate, clavate, subclavate or subcylindrical. Lamella edge heterogeneous. Cheilocystidia common, 30– 60 × 11–28 μm, (broadly) fusiform, with long or short apical projection, lageniform, or clavate. Pleurocystidia scarce, 46–68 × 25–38 µm, scattered, similar to the cheilocystidia. Pileipellis a cutis or an intermediate cutis-trichoderm, with terminal elements, 6–24 μm wide, often constricted at the septa; hyphae hyaline, or with diffuse intracellular pale brown pigment. Stipitipellis a cutis, with cylindrical hyphae, (4–)9–14(–22) μm wide. Volva composed of interwoven, cylindrical hyphae, 6–22 μm wide, with common septa. The terminal elements on the external surface have intracellular, diffuse olive green pigment. Clamp connections absent in all parts examined.

Habit, habitat, and phenology:—Subgregarious. Terrestrial, among ruderal plants, at the centre of a path next to a cereal field. June.

Distribution:—Known only from the holotype collection.

Observations:—The average spore measurements given above are calculated using only the non heart-shaped spores.

Volvariella cordispora appears in the phylogeny in a well-supported clade with V. izmirensis from Turkey, V. ptilotricha E.F. Malysheva & A.V. Alexandrova (2019: 245) from Vietnam, and two sequences identified as V. taylorii from Italy and India ( HM246491 and KU752351 ). The sequences labelled V. taylorii are very distant from the collections that we interpret here as V. taylorii . As V. taylorii has usually been interpreted as a species with a greyish fibrillose pileus, not striate at the margin, most likely the Italian collection showed these characters which are very different from those of V. cordispora which has a white pileus with a pale brown disc and a striate margin. The Indian sequence is an environmental nrITS sequence (from a soil sample) and therefore its morphological characters are unknown to us. Volvariella ptilotricha has basidiomes fully covered by long, down-like hairs (inde nomen, ptilos: feather and thrix / trichos: hair) ( Malysheva et al. 2019). Volvariella izmirensis , described here as new, has distinctly larger basidiospores (8.0 × 4.8 μm on average) with avQ = 1.70.

Many Volvariella species with a white pileus can be confused with V. cordispora , but heart-shaped spores have not been observed in any of them. Volvariella hypopithys , V. pusilla , and V. neoparvula differ by their usually smaller basidiomes and their white, ochre or yellow volva, V. murinella possesses larger spores, cheilocystidia and pleurocystidia, V. reidii has much smaller spores and larger cheilocystidia, V. strangulata is distinguished by larger basidiomes, spores, cheilo- and pleurocystidia and by the presence of caulocystidia. The newly described V. cryptica , V. globifera , V. graminicola , and V. pilosipilea possess smaller basidiomes with a pileus diameter less than 25 mm and a white volva. Additional morphological differences are summarized in Tables 1 and 2.

Figures

FIGURE 23. Volvariella cordispora. A–C. Basidiomes (AH60254, holotype). D–I. Microscopic characters (AH60254, holotype). D. Cheilocystidia; E. Pleurocystidia; F–G. Spores; H. Pileipellis; I. Volva hyphae. Bar: (D–I) = 10 µm. Photos by L.A. Parra (A–C), F. Caballero (D–I).