Caballero, Justo, L.A. Parra & G. Muñoz, 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 : 65

22. Volvariella mediterranea F. Caballero, Justo, L.A. Parra & G. Muñoz , sp. nov. ( Fig. 30 ).

MycoBank: MB 856539

Typification:— Holotype: SPAIN. Burgos, Aranda de Duero, on a bank of the Duero River, 41.673121, -3.710218, elev. 844 m, under Populus sp. , 19 September 2023, V.-J. Domingo, AH56333! (Isotype: LAP 191).

Etymology:—From the Latin “ mediterranea ” for its distribution in the Mediterranean area.

Diagnosis:—This species is characterized by the medium to large basidiomes, with a white to grey, smooth to slightly fibrillose pileus and broadly ellipsoid to cylindrical spores (Q = 1.15–2.73). The cylindrical spores are often more than 10 µm long, some up to 13 µm.

Description:— Pileus 40–140 mm diam., convex or conico-convex when young, expanding to plano-convex, with or without a low, broad umbo; surface smooth to finely fibrillose; fibrils often grouped in small squamules; sometimes with patches of universal veil, not hygrophanous, white overall, sometimes with grey or brown tinges, especially around 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 slightly irregular, concolourous. Stipe 40–140 × 10–15 mm, cylindrical, slightly widening towards the base, straight or slightly curved; surface white, sometimes with pale brown tints, smooth. Volva membranaceous, saccate, fragile, grey or grey-brown, with 2–3 lobes, sometimes with brown rhizomorphs attached at the base. Context white, thin, with slightly raphanoid smell.

Basidiospores (n=397, c=5) (6.1–)6.7–9.3(–13.6) × 4.6–6.3(–6.9) μm, avl × avw = 7.8 × 5.4 μm, Q = 1.15– 2.73, avQ = 1.47, broadly ellipsoid to cylindrical, thick-walled, with barely distinct hilar appendage. Basidia 28– 41 × 8–10 μm, mono- or tetrasterigmate, subclavate or subcylindrical. Lamella edge heterogeneous. Cheilocystidia common, (44–)51–113(–140) × (11–)17–39(–45) μm, mostly fusiform with or without an elongated apex, sometimes with bifurcate, digitate excrescence, more rarely clavate or lageniform. Pleurocystidia scarce, 49–116 × 12–45 μm, similar to cheilocystidia, but without elongated apex. Pileipellis a cutis or cutis-trichoderm, with terminal elements (7–)10–25(–30) μm wide, often constricted at the septa, hyaline or with brown pigment. Stipitipellis a cutis, or a cutis-trichoderm, with cylindrical hyphae 5–17 μm wide. Rhizomorphs with three types of hyphae: hyphae 1.5–2.8 µm wide, with scarce septa, with yellow-green pigment, clamped; hyphae 3.1–4.2 µm wide, multiseptate, thick-walled, with olive brown pigment, clamped; and thromboplerous hyphae 7.7–11.9 µm wide, that exude their contents through a porous wall. Volva composed of interwoven, cylindrical hyphae, 5–20 μm wide, with common septa; on the external surface arranged as a trichoderm. Clamp connections absent in all parts examined, except on some hyphae of the rhizomorphs.

Habit, habitat, and phenology:—Solitary or gregarious. Collected in different ecosystems including riparian forests, mixed forests with Populus sp. , Quercus ilex and Juniperus sp. , dune ecosystems under Pinus halepensis and Quercus ilex also with Ampelodesmos mauritanicus , Pistacia lentiscus and Chamaerops humilis , and in pure Quercus ilex forests on alluvial soil, with nitrogen input from livestock. Often terrestrial, but one collection made directly on a Populus trunk. June–November.

Distribution:— Spain (Burgos, La Rioja, Mallorca, Valladolid).

Additional collections examined— SPAIN. Balearic Islands: Mallorca, Pollença, Formentor, on sandy soil under Pinus halepensis with Quercus ilex , close to the beach, 22 November 2002, J.L. Siquier, JLS1605; ibid., Can Martorellet, Pollença, under Quercus ilex , 26 October 2009, J.L. Siquier, JLS2894; ibid., habitat unknown, I. Vidal & J.C. Salom, JCS1177B. La Rioja: Tudelilla, under Populus sp. , and Quercus ilex , 6 June 2009, G. Muñoz, GM1517. Valladolid: Siete iglesias de Trabancos, on a rotten trunk of Populus sp. , 1 June 1998, A.G. Blanco, M. Sanz Carazo & J.B. Del Val, MA Fungi 54717.

Observations:—The spore shape of Volvariella mediterranea ranges from broadly ellipsoid to cylindrical. The cylindrical spores are quite characteristic, and they represent about 10 % of the spore measurements above. The cylindrical spores are often more than 10 µm long, sometimes up to 13 µm, which is an uncommon character in Volvariella . The presence of rhizomorphs, with clamped hyphae, might also be a good additional character to separate this species, but this character needs further study in the genus Volvariella , so establish its value as a diagnostic character. Volvariella caesiotincta differs in the generally darker colours, larger basidiospores (6.9 × 4.9 µm on average), and the vacuolar or granular pigment in the pileipellis hyphae. Volvariella murinella differs by the smaller basidiomes (pileus less than 70 mm diam.), smaller basidiospores (7.3 × 4.7 µm on average), and lack of rhizomorphs. Volvariella taylorii has smaller basidiomes (pileus up to 40 mm diam.) and smaller basidiospores (6.9 × 4.7 µm on average). Volvariella volvacea has darker basidiomes; smaller terminal hyphae in the pileipellis, often with darker, vacuolar pigment, and it lacks rhizomorphs.

Figures

FIGURE 30. Volvariella mediterranea. A–E. Basidiomes. A–B. (AH56333, holotype); C. (GM1517); D. (JCS-1177B); E. (JLS 2894). F–M. Microscopic characters. F–G. Cheilocystidia (JSC1177B); H. Pleurocystidia (JSC1177B); I. Spores (GM1517); J–K. Pileipellis (JCS1177B); L. Stipitipellis (GM1517); M. Volva hyphae (AH56333, holotype); N. Rhizomorphs (JCS1177B). Bar: (F–I, M–N) = 10 µm; (J–L) = 100 µm. Photos by L.A. Parra (A–B), G. Muñoz (C), J.C. Salom (D), J.L. Siquier (E), F. Caballero (F–M).