Entoloma dicymbophilum Largent & T.W.Henkel, 2023

Henkel, Terry & Largent, David L., 2023, THE ENTOLOMATACEAE OF THE PAKARAIMA MOUNTAINS OF GUYANA VII: ENTOLOMA DICYMBOPHILUM SP. NOV. AND A KEY TO GUYANESE SPECIES OF ENTOLOMA S. STR., Edinburgh Journal of Botany 80 (1943), pp. 1-9 : 3-7

Entoloma dicymbophilum Largent & T.W.Henkel , sp. nov.

Similar to Entoloma fragilum Largent & Aime in its white colour but differs in its larger fleshy-fibrous basidiomata, larger basidiospores, longer basidia, and musky, clay-like odour. – Type: Guyana, Region 8 Potaro-Siparuni, Pakaraima Mountains, Upper Potaro River Basin, 2 km S of Potaro River at Tadang base camp at 5°16′14.5′′N, 59°50′39.1′′W, 710–750 m, on humic mat of forest floor under Dicymbe corymbosa and D. altsonii , 4

vi 2013, T. Henkel 9740 (holotype BRG, isotype HSC-F [ G1429 ]). MycoBank MB844000 . GenBank accession nos.: ITS = OR168649 ; 28 S = OR146595 . Figures 1 , 2 .

Basidiomata tricholomatoid. Pileus 48–110 mm broad, 11–20 mm tall, initially broadly conic with downturned, irregularly sulcate margin, with age broadly convex to uplifted with broad, rounded umbo, off-white to pale cream (4A2–4A3) throughout, glabrous, moist; context off-white, unchanging, 8–10 mm thick above stipe. Lamellae thick, subdistant, broadly sinuate with distinct decurrent teeth, initially light creamish tan with faint pinkish tones (4A3–5A3), with age dull pink, 2 mm tall at margin, 4–6 mm centrally, 3–4 mm

at stipe; edges concolorous, smooth, unchanging; lamellulae 1–3, 5–30 mm long. Stipe 95–150 × 9–20 mm, subequal, enlarging slightly and evenly towards base, curving and occasionally twisting, solid, off-white to pale orangish cream (4A3–4A4) throughout, shallowly longitudinally striate, apical 1/3 with scattered minute orangish squamules visible under hand lens; basal mycelium a dense white mat surrounding base; context off-white, unchanging, densely fibrous throughout. Odour somewhat musky, clay-like. Taste faintly acrid-astringent, slightly bitter.

Basidiospores subisodiametric to isodiametric, 6-angled; angles initially smooth and indistinct, becoming distinct with maturation; apex very slightly acute; contents multiglobular or without globules, rarely with a single globule, 6.9–8.9 × 6.2–8.6 μm (x = 7.9 ± 0.4 × 7.5 ± 0.4 μm; E = 1.0–1.2; Q = 1.1 ± 0.04; n = 75). Basidia narrowly cylindro-clavate and tapered to a narrow base, with granules at maturity, 43.1–65.1 × 6.9–10.9 μm (x = 52.9 ± 5.8 × 9.1 ± 1.1 μm; E = 4.6–8.5; Q = 5.9 ± 1.1; n = 31), 2 or 4 sterigmate; sterigmata up to 6.9 μm long (n = 21). Cheilocystidia and pleurocystidia absent. Lamellar trama 152–276 μm wide; hyphae subparallel to interwoven; cells long and narrow, 27.0–79.2 × 3.4–9.7 μm (x = 51.6 ± 13.7 × 6.7 ± 1.4 μm; E = 3.0–18.01; Q = 8.2 ± 3.1; n = 33). Pileipellis in radial section 27–65 μm thick, of tightly entangled, subpericlinal hyphae, these 3–5 μm wide; pileocystidia scattered, suberect, cylindrical, 7.0–16.0 × 1.5–4.2 μm (x = 11.4 ± 2.9 × 2.9 ± 0.8 μm; E = 2.7–5.5; Q = 4.1 ± 0.9; n = 14). Pileus trama hyphae in squash mounts relatively short and broad, 16.0–74.1 × 2.8–16.7 μm (x = 35.9 ± 13.4 × 8.6 ± 3.1 μm; E = 1.6–10.8; Q = 4.6 ±

2.1; n = 66). Stipitipellis at the stipe apex composed of scattered hymeniform clusters lacking basidia, at times with semi-erect and scattered caulocystidia, these cylindrical, rarely clavate, 10.5–21.0 × 3.0–7.0 μm (x = 15.0 ± 4.0 × 4.0 ± 2.0 μm; E = 3–5; Q = 4.0 ± 1.1; n =

5). Stipe trama hyphae subparallel and entangled in longitudinal sections; cells 19.8–97.8 × 2.9–10.3 μm (x = 47.1 ± 18.6 × 6.4 ± 1.7 μm; E = 2.5–14.7; Q = 7.5 ± 2.7; n = 57). Oleiferous hyphae very rare in the trama of the pileus, stipe and lamellae. Lipoidal globules absent. Clamp connections evident and abundant in hyphae of the subhymenium, pileus trama , lamellae and stipe.

Distribution. Known only from the type locality in the Upper Potaro River Basin of Guyana.

Habitat and ecology. In pairs on humic mat of forest floor under Dicymbe corymbosa and D. altsonii .

Etymology. Dicymbe and - philus (Greek, ‘loving’), referring to the occurrence in forests with D. corymbosa and D. altsonii .

Proposed IUCN conservation category. Data deficient (DD) due to inadequate information for the species’ geographical distribution or population status in this remote, mycologically underexplored region.

Notes. Entoloma dicymbophilum is recognised in the field by its medium to large, entirely off-white to pale-cream basidiomata with solid trama, smooth, moist pileus, thick, subdistant, sinuate, off-white to dull-pink lamellae, and clay-like musky odour. The species fits well into Entoloma s. str. based on its robust, tricholomatoid stature, isodiametric 6-angled basidiospores, narrowly cylindro-clavate basidia, broad pileus tramal hyphae, and abundant clamp connections ( Largent, 1994). The species is putatively ECM based on its inclusion in Entoloma s. str. and occurrence in forests dominated by ECM Dicymbe trees ( Largent et al., 2008).

Entoloma fragilum is another white-coloured Guyanese species with isodiametric basidiospores, but it differs from E. dicymbophilum in its smaller, brittle basidiomata, smaller basidiospores (4.9–6.8 × 4.8–6.7 vs 6.9–8.9 × 6.2–8.6 μm), shorter basidia (28.2–36.2 vs 43.1–65.1 μm), and pleasant, Lactarius -like odour ( Largent et al., 2008). The other sympatric Entoloma s. str. species in Guyana, E. olivaceocoloratum Largent & T.W.Henkel , E. rugosostriatum Largent & T.W.Henkel and E. illinitum Largent & Aime , all differ from E. dicymbophilum in their much darker olive-brown, greyish brown, or yellowish brown pileus colours, respectively, among other features ( Largent et al., 2008).

Several other tropical Entolomataceae species are known with tricholomatoid statures and entirely white basidiomata. These include Entoloma leviculum Corner & Horak from Sabah, which can be differentiated from E. dicymbophilum by its lack of odour and smaller overall size, with the pileus 15–25 mm broad and the stipe 30–50 × 3–5 mm ( Horak, 1980). The Antillean Entoloma cerrusatum Pegler , E. bakeri Dennis ( Pegler, 1983) , Malagasy E. vetulum (Romagn.) Noordel. & Co-David ( Romagnesi, 1941) , and West African E. candicans (Romagn. & Gilles) Noordel. & Co-David and E. eburneum (Romagn. & Gilles) Noordel. & Co-David (Romagnesi & Giles, 1979) are white and tricholomatoid but each differ from E. dicymbophilum in their heterodiametric basidiospores that are> 8.5 μm long. The Cameroonian Entoloma intricatum Largent, T.W.Henkel & R.A.Koch has large, off-white basidiomata but differs from E. dicymbophilum in its naucorioid stature with adnate lamella attachment and strongly heterodiametric, 5- to 7-angled basidiospores ( Largent et al.,

2020). Among white Neotropical Alboleptonia species described from Guyana or Panama,

all differ from Entoloma dicymbophilum in their slender, collybioid or clitocyboid statures and heterodiametric basidiospores ( Henkel et al., 2010b; Reschke et al., 2022). Brazilian Entoloma species with isodiametric basidiospores similar to those of E. dicymbophilum differ in numerous other macro- and micromorphological features ( Coimbra et al., 2013).

Key to species of Entoloma s. str. known from the Pakaraima Mountains of

Guyana

1a. Pileus off-white to pale cream–coloured ___________________________________________ 2

1b. Pileus olive-brown, greyish brown, or yellowish brown ______________________________ 3

2a. Pileus 50–62 mm broad, dry; odour fragrant, pleasant, Lactarius -like _______ E. fragilum

2b. Pileus 48–110 mm broad, moist; odour unpleasant, musky, clay-like ___ E. dicymbophilum

3a. Pileus yellowish brown; odour radish-like __________________________________ E. illinitum

3b. Pileus olive-brown or greyish brown; odour mild, not radish-like _____________________ 4

4a. Pileus olive-brown,> 90 mm in diameter; margin not striate ______ E. olivaceocoloratum

4b. Pileus greyish brown, <50 mm in diameter; margin striate __________ E. rugosostriatum

Figures

Figure 1. Entoloma dicymbophilum Largent & T.W.Henkel, sp. nov. A, Field habit, off-white to cream basidiomata with exposed lamellae, Upper Potaro Basin, Guyana; B, immature basidioma (lateral view). Each scale bar, 20 mm. Photographs of the holotype, Henkel 9740, taken by Todd Elliott (A) and Terry Henkel (B).

Figure 2. Microscopic features of Entoloma dicymbophilum Largent & T.W.Henkel, sp. nov. A, basidiospores; B, basidia and basidioles; C, pileipellis and subtending trama; D, pileus trama. All photographs of the holotype, Henkel 9740, taken by D. L. Largent. Scale bars: A and B, 10 μm; C and D, 50 μm.