Pluteus purpureofuscus Jiang Xu, T.H. Li & Z.W. Ge, 2015

Xu, Jiang, Li, Tai Hui, Justo, Alfredo & Ge, Zai Wei, 2015, Two new species of Pluteus (Agaricales, Pluteaceae) from China, Phytotaxa 233 (1), pp. 61-68 : 65-67

Pluteus purpureofuscus Jiang Xu, T.H. Li & Z.W. Ge , sp. nov. Fig. 2 d , Fig. 4

MycoBank: MB 812365; Fungal Name: FN570174.

Diagnosis:— Differing from Pluteus subcervinus in having purple pileus, relatively bigger basidiospores and habitat on coniferous wood

Type: — CHINA, Sichuan Province, Mianning County, Lamagetou Nature Reserve , elev. 3110 m, at 28°56′07″N, 102°12′42″E, 12 July 2005, Z. W. Ge 460, HKAS48956 (Holotype; nrITS: KR350489 ) .

Etymology: —the epithet purpureofuscus is from the Latin words of “ purpureus ” (purple) and “ fuscus ” (dark colored), making reference to the dark purple color of the pileus.

Pileus 40–60 mm in diam., subconical to convex, fleshy, purple to dull purple (13C4–13D4), slightly paler towards the margin (15C6), not hygrophanous, innately or conspicuously radially fibrillose; margin thin, non-striate. Lamellae free, white when young, becoming pinkish, slightly ventricose, crowded, with lamellulae of 1–2 lengths; lamellar edge slightly eroded, dark-brown for whole length or only in some areas. Stipe 50–70 × 4–7 mm, cylindrical to subcylindrical, central, equal with a slightly enlarged base, curved, pale purplish brown (15C4–15D4), longitudinally striate, slightly pubescent or fibrillose, solid. Context in pileus and stipe white, unchanging when injured. Taste and odor not recorded.

Basidiospores (40/3/1) 6.0–8.0(–9.0) × 5.0–6.0(–6.5) μm, avl × avw = 7.4 × 5.5 μm, Q = 1.20–1.60, avQ = 1.34, broadly ellipsoid to ellipsoid, smooth, slightly thick-walled. Basidia 21–40 × 7–10 μm, 4-spored, clavate or cylindrical, colorless, thin-walled, sterigmata 3–4 μm long. Pleurocystidia 55–80 × 12–30 μm, abundant, metuloid, fusoid-ventricose or lageniform with 2–4 apical or subapical horns, occasionally with fewer or without horns; horns sometimes forked; wall thickened in upper half (2.0–2.8 μm thick at neck), smooth, colorless or with pale brown intracellular pigment. Intermediate cystidia rare, predominantly fusiform and without apical hooks, sometimes similar to the pleurocystidia but smaller and/or with thinner walls. Lamellar edge sterile. Cheilocystidia abundant, 30–58 × 10–20 μm, subclavate to clavate, thin-walled, with or without brown intracellular pigment. Hymenophoral trama convergent; hyphae 3–12 μm in diam., hyaline, smooth, thin-walled. Pileipellis a cutis, with cylindrical hyphae 5–18 μm wide, filled with grayish red to reddish brown (8C4–8D4) intracellular pigment in 5% KOH; terminal elements 98–230 μm long, sub-cylindrical, usually tapering towards an obtuse apex. Stipitipellis a cutis; hyphae 4–10 μm wide, cylindrical, colorless or with brown content, thin-walled. Caulocystidia absent. Clamp connections present in hyphae of pileipellis and stipitipellis.

Habit, habitat and distribution: —Solitary to scattered. On rotten logs of Picea sp. in meadow with shrubs and remnant trees apparently once forested. Asia: Known only from Hengduan Mountains of southwest China.

Discussion: —The cutis pileipellis, the metuloidal hymenial cystidia, together with the molecular data ( Fig. 1 ), place Pluteus purpureofuscus in section Pluteus . It is characterized by the combination of the (i) medium sized basidiomes with convex to plano-convex dark purpure pileus; (ii) curved and pale purplish brown stipe; (iii) pileipellis elements contained with grayish red to reddish brown intracellular pigment; (iv) subglobose to broadly ellipsoid spores sized 6.0–8.0(–9.0) × 5.0–6.0(–6.5) μm; (v) cheilocystidia clavate and filled with brown intracellular pigment; (vi) obvious clamp connections; (vii) and habitat on coniferous wood.

On the molecular study, P. subcervinus (KJ009752) appears to be the closest relative taxa of P. purpureofuscus ( Fig. 1 ). However, P. subcervinus is distinct by its brown pileus, smaller basidiospores (5.4–8.5 × 4.4–5.5 μm, avl × avw = 6.9 × 5 μm) ( Justo & Castro 2007a), and habitat on angiosperm wood. Pluteus subcervinus is only known with certainty from Sri Lanka and India ( Pegler 1977, 1986, Pradeep et al. 2002). An additional record from China remains to be confirmed with molecular and/or morphological data ( Bi et al. 1993).

All known members of the salicinus clade, which appear close in the phylogeny ( Fig. 1 ), lack the purple-brown coloration and habitat mostly on angiosperm wood. The two species of the salicinus clade found on coniferous wood include P. sepiicolor E.F. Malysheva ( Justo et al. 2014: 64) and P. oreibatus Justo ( Justo et al. 2014: 66). However, both species differs from the present taxon by the brown pileus and the white lamellar edges. Aomong the compared species with coniferous habit, mainly in the pouzarianus and atromarginatus clades ( Fig. 1 ), none of them has any purple coloration and habitat at high elevation above 3000 m as P. purpureofuscus ; besides, their basidiospore, cheilocystidia and geographic distribution are also different ( Justo et al. 2014).

Among the other known species, two species of Pluteus section Hispidoderma , viz. Pluteus hispidilacteus Horak (2008: 22) and P. decoloratus Horak (2008: 24) , also can develop pink colors on the pileus with age but they are clearly different from P. purpureofuscus in the non-metuloid and absent to very rare pleurocystidia. Besides, they are only known from New Zealand ( Horak 2008). Pluteus lilacinus (Sacc.) Singer (1961: 337) , with lilac or purplish brown to cocoa brown pileus, is somewhat morphologically similar and also belongs to Pluteus section Pluteus , but it is distinctive by its glabrous pileus, smaller basidiospore 5–7.5 × 3.5–5.7 μm, more elongate and narrower cheilocystidia 40–75 × 5.5–8.8 (–12) μm, the mainly Magnus - type pleurocystidia 42–70 × 9.5–16 μm with sharply acute apex, and absence of clamp connections ( Singer 1961).

Figures

FIGURE 1. Best tree from the ML analysis of the nrITS dataset of selected Pluteus sect. Pluteus species. Support values are given on or below the branches.

FIGURE 2. a–c.Basidiomata of P.griseodiscus (b, c. GDGM42280, d. GDGM42377).d.Basidiomata of P.purpureofuscus (HKAS48956– holotype, photo by Z.W. Ge.). Scale bars: a, b, c, d = 1 cm.

FIGURE 4. Pluteus purpureofuscus (HKAS48956–holotype). a. Basidiospores. b. Basidia. c. Cheilocystidia. d. Pleurocystidia. e. Intermediate cystidia. f. Pileipellis elements. Scale bars: a = 5 μm; b = 10 μm; c, d, e, f = 20 μm.