Russula spectabilis Manz, F. Hampe & Buyck, 2025

Manz, Cathrin, Amalfi, Mario, Buyck, Bart, Hampe, Felix, Yorou, Nourou S., Adamčík, Slavomír & Piepenbring, Meike, 2025, Just the tip of the iceberg: uncovering a hyperdiverse clade of African Russula (Basidiomycota, Russulales, Russulaceae) species with signs of evolutionary habitat adaptations, IMA Fungus 16, pp. e 140321-e 140321 : e140321-

Russula spectabilis Manz, F. Hampe & Buyck , sp. nov.

Figs 32 , 33 , 34

Holotype.

Benin. Atakora, Kossoucoingou , co-ord. 10°9.9'N, 1°12.1'E, alt. 500 m, Sudanian woodland, under Isoberlinia tomentosa , on rocky soil, 20. 07. 2021, leg. C. Manz, F. Hampe, G. Abohoumbo, T. C. Bogo, CM-21-154 (holotype B 70 0105435 , isotype UNIPAR).

Additional material examined.

Benin. Atakora, Natitingou, Kota Waterfalls , co-ord. 10°12.7'N, 1°26.8'E, alt. 500 m, Sudanian woodland, under I. tomentosa , on rocky soil, 12. 07. 2021, leg. C. Manz, F. Hampe, N. S. Yorou & G. Abohoumbo, CM-21-116 (paratype, B 70 0105436 , UNIPAR) .

Diagnosis.

Basidiomata relatively robust, pileus surface yellow-orange, taste mild, terminal cells of the pileipellis hyphae lanceolate near the pileus margin and narrowly cylindrical near the pileus centre, occurring in savannah woodlands. Differs from Russula aureola Buyck by a lower spore ornamentation.

Description.

Growth habit: basidiomata solitary. Pileus: medium-sized to large, 80–90 mm in diam., soon expanding plane, centrally depressed; margin even, finely tuberculate-striate up to 10 mm, regularly shaped; cuticle smooth, matt, peelable up to ¾ of the pileus radius, colour butter yellow (4 B 5), near the margin pale orange (5 A 3) or light orange (5 A 4), near the centre, melon (5 A 6) or golden yellow (5 B 7). Lamellae: 6–7 mm wide, 8–9 lamellae present along 1 cm near the pileus margin, narrowly adnate, white to pale cream, furcations frequent at the stipe attachment, anastomoses absent, lamellulae occasionally present; edges entire, concolourous. Stipe: 90–100 × 18–22 mm, cylindrical, smooth to slightly rugose, annulus absent, white; cottony stuffed, cavernate with 2–3 distinct chambers. Context: 6–7 mm thick at half pileus radius, white, unchanging when bruised, brittle, taste mild, odour inconspicuous to pleasant, macrochemical reactions: guaiac after 8–10 seconds (++) on stipe and weakly positive (+) on lamellae surfaces, FeSO 4 weak salmon orange, sulphovanillin negative, KOH negative or slightly discolouring on the pileipellis, phenol negative. Spore print: not observed, probably white or cream.

Spores: (6.9 –) 7.4–7.7 – 8.1 (– 8.7) × (6.1 –) 6.4–6.7 – 7 (– 7.4) µm (n = 60), Q = (1.03 –) 1.10–1.15 – 1.20 (– 1.26), subglobose to broadly ellipsoid; ornamentation of moderately distant, dense to very dense, pustules [(5 –) 6–9 (– 12) in a circle of 3 µm diam.], not well defined, by light microscopy up to 0.5 µm high, connected by abundant, short lines [(2 –) 3–6 (– 8) in the circle] forming a complete reticulum, isolated or partially connected elements very rare to absent, occasionally to frequently fused (approx. 1–4 fusions in the circle); suprahilar plage small, inamyloid, without ornamentation. Basidia: (36.5 –) 42–47.5 – 53 (– 58) × (9 –) 10–11 – 12 (– 12.5) µm (n = 40), narrowly to broadly clavate, 4 - spored; basidiola approx. 5–8 µm wide, cylindrical to clavate. Hymenial cystidia: on lamellae sides (60.5 –) 71–83.5 – 95.5 (– 114) × (8.5 –) 9.5–10.5 – 11.5 (– 12.5) µm (n = 40), predominantly lanceolate, sometimes with slight moniliform constrictions, originating in subhymenium and somewhat protruding over basidia, thin-walled, apically obtuse, usually with a 2–13 µm long appendage; heteromorphous contents moderately dense, mostly amorphous, rarely crystalline, mostly located in the upper two-thirds, not reacting to sulphovanillin. Hymenial cystidia near the lamellae edges distinctly shorter and narrower, (38.5 –) 42.5–51 – 60 (– 70) × (6 –) 6.5–7.5 – 9 (– 11) µm (n = 40), lanceolate or rarely cylindrical, apically predominantly mucronate, with broad, 2.5–11 µm long appendages; heteromorphous contents similar to the one in hymenial cystidia on lamellae sides, but less dense. Lamellae edges: sterile, consisting of cystidia and marginal cells. Marginal cells: (23.5 –) 27.5–32.5 – 38 (– 48.5) × (4 –) 4.5–5.5 – 6.5 (– 8) µm (n = 40), narrowly utriform, lageniform or lanceolate, rarely cylindrical with slight constrictions, sometimes with a forked apex, optically empty, thin-walled. Pileipellis: orthochromatic in Cresyl blue, gradually passing to the underlying context, 125–165 µm deep; suprapellis a trichoderm, 30–40 µm deep, composed of erect hyphal terminations; gradually passing to a 95–130 µm deep subpellis of loose, strongly gelatinised, intricate, irregularly orientated, 1.5–4 µm wide hyphae, becoming denser and horizontally arranged near the context. Acid resistant incrustations absent. Hyphal terminations: near the pileus margin composed of 1–4 unbranched cells, thin-walled, frequently covered with a glutinous coating well visible in Congo red, terminal cells (8 –) 11.5–19.5 – 27 (– 40) × (2 –) 2.5–3 – 3.5 (– 4.5) µm (n = 60), predominantly lanceolate or subulate, rarely cylindrical, apically obtuse or acute; subterminal cells usually shorter, 3–6 µm wide, cylindrical or slightly inflated, branched or not. Hyphal terminations near the pileus centre composed of 1–3 unbranched cells, thin-walled, terminal cells shorter, (6.5 –) 9–13 – 17 (– 26) × 2–2.5 – 3 (– 3.5) µm (n = 61), slender, straight, cylindrical; subterminal cells equally long, 2–3.5 µm wide. Pileocystidia: near the pileus margin (15 –) 27–37.5 – 47.5 (– 55.5) × (3 –) 3.5–4.5 – 5.5 (– 7.5) µm (n = 44), one-celled, cylindrical or clavate to subcapitate, rarely lanceolate, flexuous, slightly moniliform, originating in the suprapellis, thin-walled, occasionally with a 2–3 µm long appendage; heteromorphous contents amorphous, not reacting to sulphovanillin. Pileocystidia near the pileus centre similar in size, shape and heteromorphous contents to those near the pileus margin, (24.5 –) 32–40 – 48.5 (– 55) × (4 –) 4.5–5 – 5.5 (– 6.5) µm (n = 40). Context: without cystidioid hyphae, oleiferous hyphae dispersed.

Etymology.

Reference to the African plant Costus spectabilis (Fenzl) K. Schum. , the flower of which is similarly coloured.

Distribution and ecology.

Only known from the Sudanian woodlands in Atakora in Benin.

Notes.

Russula aureola , Russula bonii Buyck and Russula singeri R. Heim , are other tropical African species with similar orange pileus colours. Russula aureola has more slender basidiomata and was described from Gilbertiodendron dewevrei forests in the DRC, differing by a high spore ornamentation of 2 µm long spines and a pileipellis with attenuated terminal cells on top of a chain- of barrel-shaped subterminal cells ( Buyck 1994). Russula bonii has relatively robust basidiomata with low spore ornamentation. It is known from miombo woodland in Zambia ( Buyck 1995). It was placed in subsect. Amoeninae Singer ex Buyck because of the absence of both hymenial cystidia and pileocystidia ( Buyck 1995). Russula singeri is a mild species with white spore print which differs by a relatively tough, greying stipe and spores with an amyloid suprahilar plage ( Heim 1937, 1938). Russula tenuithrix Buyck has a similar pileipellis structure and low spore ornamentation of up to 0.5 µm height, but differs by its greenish-grey pileus colours ( Harkönen et al. 1993). Based on type sequencing, it is not related to R. spectabilis and probably belongs to Russula subgen. Malodorae Buyck & V. Hofstetter. The type sequence of R. tenuithrix will be published in a future study on subgen. Malodorae.

Figures

Figure 32. Russula spectabilis A, B field pictures of basidiomata: A CM- 21-154, holotype, B CM- 21-116; C, D scanning electron microscopical pictures of basidiospores (both CM- 21-154, holotype). Scale bars: 2 cm (A, B); 3 µm (C, D).

Figure 33. Hymenial elements of Russula spectabilis (holotype, CM- 21-154) A basidia and basidiola, B hymenial cystidia near the lamellar edges, C marginal cells, D hymenial cystidia, E spores as seen in Melzer’s reagent. Scale bar: 10 μm, but only 5 μm for spores.

Figure 34. Elements of the pileipellis of Russula spectabilis (holotype, CM- 21-154) A, B elements near the pileus centre: A hyphal terminations, B pileocystidia; C, D elements near the pileus margin: C hyphal terminations, D pileocystidia. Scale bar: 10 μm.