Russula florae Manz & F. Hampe, 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 florae Manz & F. Hampe , sp. nov.

Figs 18 , 19 , 20

Holotype.

Benin. Atakora, Natitingou, Kota Waterfalls , co-ord. 10°12.7'N, 1°26.8'E, alt. 500 m, in a gallery forest, under Uapaca guineensis on rocky soil, 10. 07. 2021, leg. C. Manz, F. Hampe, CM-21-098 (holotype B 70 0105422 , isotype UNIPAR).

Additional material examined.

Benin. Atakora, Natitingou, Kota Waterfalls , co-ord. 10°12.8'N, 1°26.8'E, alt. 500 m, in a gallery forest, under U. guineensis & Berlinia grandiflora , directly along the riverside on bare sand, 11. 07. 2021, leg. C. Manz, F. Hampe, N. S. Yorou, G. Abohoumbo & D. Dongnima, CM-21-109 (paratype, B 70 0105423 , UNIPAR) ; ibid. 14. 07. 2021, leg. C. Manz, F. Hampe, N. S. Yorou, G. Abohoumbo & D. Dongnima, CM-21-121 (paratype, B 70 0105424 , UNIPAR) ; ibid. 19. 07. 2021, leg. C. Manz, F. Hampe, N. S. Yorou, G. Abohoumbo & D. Dongnima, CM-21-145 (paratype, B 70 0105425 , UNIPAR) ; ibid. leg. N. S. Yorou, CM-21-160 / SYN 5074 (paratype, B 70 0105426 , UNIPAR) ; ibid. co-ord. 10°12.7'N, 1°26.6'E, alt. 500 m, in a gallery forest, under U. guineensis & B. grandiflora , directly along the riverside in between fine gravel, 15. 06. 2022, leg. C. Manz, F. Hampe, S. Sarawi, A. Rühl & D. Dongnima, CM-22-178 (paratype, B 70 0105427 , UNIPAR) ; ibid. 17. 06. 2022, leg. C. Manz, F. Hampe, S. Sarawi, A. Rühl & D. Dongnima, CM-22-185 (paratype, B 70 0105428 , UNIPAR) ; ibid. 06. 07. 2022, leg. C. Manz & F. Hampe, CM-22-284 (paratype, B 70 0105429 , UNIPAR) .

Diagnosis.

Relatively small, pileus surface pinkish and cracking into fine areolae, stipe without annulus, context fragile, taste mild, hyphal terminations in pileipellis arranged in erect tufts, occurring in gallery forests. Differs from R. roseoalba by its negative reaction to guaiac.

Description.

Growth habit: basidiomata solitary or in small groups of up to five. Pileus: small to medium-sized, 10–40 mm in diam., when young hemispherical, truncated, with margins touching the stipe, later expanding plane, when mature, centrally depressed; margin even or slightly involute, distinctly tuberculate-striate up to ¾ of the pileus margin, frequently slightly to distinctly radially cracked up to ½ of the pileus radius, mostly crenulate, sometimes undulate, usually with crown of fugitive partial veil remnants; cuticle matt, very finely areolate, hardly peelable, colour near the margin white, pinkish-white (10-11 A 2) or reddish-grey (10 B 2), becoming gradually darker towards the centre, rosewood (9 D 5), dull red (10 B 3), brownish-red (10 C 6), reddish-grey (11 B 2) or violet brown (10 E 5), occasionally with greyish-green (30 B 4) spots. Lamellae: 2–3 mm wide, 6–7 lamellae present along 1 cm near the pileus margin, narrowly adnate, white, occasionally forked, low anastomoses only at the pileus margin, lamellulae absent; edges entire, concolourous. Stipe: 25–35 × 3–5 mm, cylindrical, somewhat bulging here and there, smooth to slightly rugose, annulus absent, white; hollow. Context: approx. 1 mm thick at half pileus radius, white, unchanging when bruised, brittle, taste mild, odour inconspicuous; macrochemical reactions: guaiac after 8–10 seconds negative on both stipe and lamellae surfaces, FeSO 4 salmon orange, sulphovanillin, KOH and phenol negative. Spore print: not observed, but probably white or cream.

Spores: (6.8 –) 7.2–7.6 – 8 (– 8.8) × (6.3 –) 6.8–7.2 – 7.6 (– 8.7) µm (n = 90), Q = (1 –) 1.02–1.06 – 1.09 (– 1.17), subglobose, rarely broadly ellipsoid; ornamentation of distant to moderately distant amyloid warts [(2 –) 3–5 (– 6) in a circle of 3 µm diam.], 1–1.8 µm high, connected by frequent to abundant lines [(1 –) 2–4 (– 5) in the circle] forming a complete reticulum, rarely fused (up to 1 fusion in the circle), warts frequently rimmed by additional smaller warts visible only by SEM; suprahilar plage small, inamyloid, without ornamentation. Basidia: (32 –) 35–39 – 43 (– 48) × (10 –) 11–12.5 – 14.5 (– 20) µm (n = 60), clavate to subclavate, 4 - spored; basidiola approx. 5–10 µm wide, cylindrical to clavate. Hymenial cystidia: on lamellae sides (61 –) 70.5–81 – 91.5 (– 114) × (7 –) 9.5–12 – 14.5 (– 20) µm (n = 61), predominantly fusiform, rarely subclavate, originating in subhymenium and somewhat protruding over basidia, thin-walled, usually with a 3–15 µm long appendage, rarely with 2 appendages; heteromorphous contents amorphous, mostly located in the upper third, not reacting to sulphovanillin. Hymenial cystidia near the lamellae edges distinctly shorter, (37.5 –) 44–51.5 – 59 (– 70.5) × (8 –) 10–11.5 – 13 (– 15) µm (n = 60), similar in shape to hymenial cystidia on lamellae sides; heteromorphous contents only located near the apex, distinctly less dense. Lamellae edges: fertile, with equal representation of cystidia, basidia, basidiola and marginal cells. Marginal cells: (10 –) 14.5–19.5 – 24 (32.5) × (4 –) 5.5–7 – 8.5 (– 11) µm (n = 60), not well differentiated, variable in shape, cylindrical, clavate, pyriform, utriform or fusiform, sometimes hard to distinguish from basidiola, optically empty, thin-walled. Pileipellis: orthochromatic in Cresyl blue, sharply delimited from the underlying context, 145–185 µm deep; suprapellis a trichoderm, 35–50 µm deep, not gelatinised, composed of erect hyphal terminations; well delimited from the 100–145 µm deep subpellis of loose, irregularly orientated, interwoven, strongly gelatinised, 4–9 µm wide hyphae, becoming denser and horizontally arranged near the context. Acid resistant encrustations absent. Hyphal terminations: near the pileus margin arranged in erect tufts corresponding to the fine, macroscopically visible areolae, composed of (1 –) 3–4 unbranched cells, thin-walled, terminal cells (15.5 –) 24.5–30 – 36 (– 44) × (3 –) 4–5 – 5.5 (– 6.5) µm (n = 90), subulate, rarely subcylindrical, apically obtuse; subterminal cells shorter, 3.5–9 µm wide, cylindrical or ellipsoid. Hyphal terminations near the pileus centre similar to the ones near the pileus margin, terminal cells shorter, (9.5 –) 15–22 – 29 (– 39) × (3 –) 4–4.5 – 5.5 (– 6.5) µm (n = 91), more frequently cylindrical; subterminal cells shorter, 3.5–8 µm wide, cylindrical or ellipsoid. Pileocystidia: near the pileus margin (23.5 –) 30.5–36 – 42 (– 53.5) × (2 –) 4–4.5 – 5 (– 5.5) µm (n = 29), rare, one-celled, predominantly fusiform, rarely cylindrical, originating in the suprapellis, thin-walled, apically obtuse, sometimes with a 1–3.5 µm long appendage; heteromorphous contents amorphous, sometimes only located in the apical part, clearly discernible in sulphovanillin, content insensitive, but cytoplasm turning to darker pink, also in the neighbouring cell. Pileocystidia near the pileus centre more frequent, similar in size, shape and heteromorphous contents to the ones near the pileus margin, (20.5 –) 32–39.5 – 47 (– 59) × (3 –) 4–4.5 – 5.5 (– 6.5) µm (n = 62). Context: without cystidioid and oleiferous hyphae.

Etymology.

For Flora, the daughter of the authors of this species.

Distribution and ecology.

Only known from the Kota gallery forest in Benin.

Notes.

Basidiomata of R. roseoalba without the fugitive fragile annulus are similar in field aspect to basidiomata of R. florae . The former species can be distinguished by its strongly positive reaction to guaiac and smooth pileipellis which is not regularly cracking in fine scales ( Buyck 1994). Based on phylogenetic analyses, R. roseoalba is so far only known from the holotype collection. Russula acriuscula Buyck is another species with pinkish-white pileus colours, but, as a member of subgen. Russula (subsect. Echinospermatinae Buyck), it is unrelated to “ Afrovirescentinae ”. It can be distinguished from R. florae by its acrid taste, more robust basidiomata and spores with isolated spines and amyloid suprahilar spot. Russula pruinata Buyck has a red pileus surface, but it can have whitish-farinaceous scales (probably from veil remnants) and also differs by its distinctly yellowing stipe context when bruised ( Buyck 1994).

Figures

Figure 18. Russula florae A – F field pictures of basidiomata: A CM- 21-098, holotype, B CM- 21-109, C CM- 21-121, D CM- 21-145, E CM- 22-185, F CM- 22-284; G, H scanning electron microscopical pictures of basidiospores (both CM- 21-093, holotype). Scale bars: 1 cm (A – F); 3 µm (G, H).

Figure 19. Hymenial elements of Russula florae (holotype, CM- 21-098) 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 20. Elements of the pileipellis of Russula florae (holotype, CM- 21-098) 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.