Clitopilus parasiticus S. P. Jian, X. Chen & Z. H. Zhang, 2025

Jian, Sipeng, Chen, Xia, Yang, Tianwei, Xu, Xinjing, Gao, Feng, Fang, Yiwei, Liu, Jing & Zhang, Chunxia, 2025, Biotrophic and saprophytic fungi from the Rhodocybe - Clitopilus clade (Entolomataceae): two new species and one now record in subtropical China, MycoKeys 116, pp. 227-254 : 227-254

Clitopilus parasiticus S. P. Jian, X. Chen & Z. H. Zhang sp. nov.

Figs 1 , 3 e – h , 4 d – f , 5 a – c

Holotype.

China • Jiangsu Province, Nanjing City, Zijinshan , E 118.83, N 32.08, alt. 32 m, scattered on soil, in the mixed broadleaf (i. e. Quercus variabilis , Robinia pseudoacacia , Osmanthus fragrans , Broussonetia papyrifera , Ilex latifolia and Yulania sp. ) forest, 15 August 2024, collected by X. Chen and Z. H. Zhang, CX 966 ( KUN-HKAS 145336 ). GenBank: ITS = PQ 793169; LSU = PQ 781613; RPB 2 = PQ 788398 .

Etymology.

“ parasiticus ” is proposed by its biotrophic behaviour.

Diagnosis.

Clitopilus parasiticus is similar to C. hobsonii , but differs by the tomentose pileus, explanate margin and smaller basidiospores.

Description.

Basidiomata pleurotoid to conchoid, small size. Pileus 2–8 mm, convex; surface whitish (# b 4 c 4 cb) to chalk white (# e 3 edf 3), with fine tomentose texture usually extending beyond the margin and densely woolly-tomentose at the base; margin typically applanate; context less than 1 mm thick. Lamellae meeting at an excentric point, whitish (# c 6 d 4 d 3) to yellowish-white (# d 3 dad 4) to yellowish (# dac 7 ac), slightly dense or crowded, edges entire and concolorous, lamellulae numerous. Stipe absent or very short, eccentric to lateral, measuring 1–2 × 0.2–0.5 mm, concolorous with lamellae. The base with white (# dddddf) mycelium. Odour none.

Basidiospores (5) 5.5–8.5 × 3.5–5.0 (5.5) μm, L m × W m = 6.6 (± 0.63) × 4.2 (± 0.34) μm, Q = 1.20–1.90 (Q avg = 1.55 ± 0.13) [186 / 9 / 3], hyaline, ellipsoid to broadly fusiform, subovoid in profile and face view, slightly angled in polar view, with 7–9 inconspicuous or obscure longitudinal ridges in total. Basidia 16–23 × 6–9.5 μm, clavate, hyaline, 4 - spored, rarely 2 - spored; sterigmata 2–3 μm. Lamellar trama subregular, composed of thin-walled, hyaline, cylindrical hyphae with a diameter of 2.5–9 μm. Lamellae edges fertile. Pleurocystidia and cheilocystidia absent. Pileipellis a cutis composed of sparsely arranged, thin-walled, hyaline, smooth, interwoven, cylindrical hyphae with a diameter of 3–5 μm, sometimes featuring erect hyphae; crystals present around the hyphae, square to subsquare, measuring 3 × 3 μm to 14 × 15 μm in area; pileal trama subregular, composed of hyaline, filamentous, thin-walled hyphae, with a diameter of 3–7.5 μm. Clamp connections absent.

Ecology and distribution.

Solitary, scattered on soil, lignicolous or gregariously living on leaves of plants ( Dryopteris sp. and Oplismenus undulatifolius ) in the mixed broadleaf forest, distributed in Jiangsu Province, China, in August.

Additional specimens examined.

China • Jiangsu Province, Nanjing City, Zijinshan , alt. 48 m, dispersedly or gregariously lignicolous or living on twigs or leaves of Oplismenus undulatifolius , in the mixed broadleaf (i. e. Quercus variabilis , Quercus aliena , Cunninghamia lanceolata , Symplocos tanakana , Celtis sinensis and Ilex cornuta ) forest, 16 August 2023, collected by X. Chen and Z. H. Zhang, CX 628 ( KUN-HKAS 145335 ) ; same places, alt. 48 m, dispersedly or gregariously living on leaves of Dryopteris sp. , 16 August 2024, collected by X. Chen and Z. H. Zhang, CX 967 ( KUN-HKAS 145337 ) .

Notes.

Clitopilus parasiticus belongs to Clitopilus sect. Scyphoides (Fig. 1 ). This new taxon is similar to C. hobsonii , C. daamsii , C. passeckerianus , C. pinsitus and C. baronii . Clitopilus hobsonii was originally described from Britain and exhibits both saprophytic and parasitic abilities. It resembles C. parasiticus in its living habits and the shape of its basidiomata, but differs from the latter by its involute or inflexed margins of the pileus and larger basidiospores (L m × W m = 7.5 × 5 μm) ( Orton 1960; Noordeloos 1984; Noordeloos 1988). Meanwhile, C. daamsii was also similar to C. parasiticus in outline; however, it differs due to its xylogenous or mycoparasitic behaviour, involute margin of pileus and larger basidiospores (8–11.5 × 4.8–6.6 μm) ( Noordeloos 1984). Another closely-related species is C. passeckerianus , which has sessile basidiomata and a white pileus. However, the habit of growing on mushroom-beds, basidiomata size (8–40 mm), the reniform to spathulate shape of the pileus and larger basidiospores (7–9 × 4–5 μm) of C. passeckerianus significantly differs from C. parasiticus ( Pilát 1935; Noordeloos 1993). Clitopilus pinsitus was first collected from Sweden and was found growing on the trunk of Quercus . This species is characterised by its spatulate, white pileus (15–40 mm) and ellipsoidal to amygdaliform basidiospores (7.5–9 × 4.6–5.3 μm) with 7–8 obscure longitudinal ridges ( Josserand 1937; Singer 1946 a). Lastly, C. baronii , recently described by Consiglio and Setti (2019) in Marmirolo, Italy, resembles C. parasiticus , but can be differentiated by its larger pileus (5–40 mm) and basidiospores (L m × W m = 7.6 × 5.0 μm), as well as its lageniform cheilocystidia.

Figures

Figure 1. Phylogenetic relationships amongst representative species of Clitopilus were inferred from a multigene dataset (ITS - LSU - RPB 2 - TEF 1) using both ML and BI methods (only shown the ML tree). Supported branches indicate bootstrap supports (BS > 50 %) and posterior probabilities (PP> 0.90). Sequences from type specimens (holotype, epitype or isotype) are marked, while new and new record taxa are highlighted in red. The abbreviations ILRT stand for: I = ITS, L = LSU, R = RPB 2 and T = TEF 1.

Figure 3. Basidiomata of Clitopilus and Rhodocybe a – d Clitopilus baronii (a, b KUN-HKAS 145333; c, d KUN-HKAS 145334) e – h Clitopilus parasiticus (e KUN-HKAS 145336, holotype; f, g KUN-HKAS 145335; h KUN-HKAS 145337) i – k Rhodocybe zijinshanensis (KUN-HKAS 145338, holotype). Scale bar: 5 mm.

Figure 4. Basidiospores and crystals of Clitopilus and Rhodocybe reveal by SEM a – c Clitopilus baronii (KUN-HKAS 145334) d – f Clitopilus parasiticus (KUN-HKAS 145336, holotype) g, h Rhodocybe zijinshanensis (KUN-HKAS 145338, holotype) i the crystals around the hyphae in pileipellis of Clitopilus parasiticus (KUN-HKAS 145336, holotype). Scale bar: 2 μm.

Figure 5. Microscopic features of Clitopilus parasiticus (KUN-HKAS 145336, holotype) a basidiospores b hymenium and subhymenium c pileipellis. Scale bars: 5 μm (a); 10 μm (b); 20 μm (c).