Pluteus salicinus Justo, Malysheva, Bulyonkova, Vellinga, Cobian, Nguyen, Minnis & Hibbett, 2014, sp. nov.
Creators: name: Justo, Alfredo
name: Malysheva, Ekaterina
name: Bulyonkova, Tatiana
name: Vellinga, Else C.
name: Cobian, Gerry
name: Nguyen, Nhu
name: Minnis, Andrew M.
name: Hibbett, David S.
Publisher: name: Zenodo
Year: 2014
Subjects: Biodiversity
Taxonomy

description: Pluteus salicinus (Pers.: Fr.) Kummer (1871: 99). Fig. 27   
 Basionym: Agaricus salicinus Persoon (1798: 9); Agaricus salicinus Persoon: Fries (1821: 202). To the best of our knowledge, no holotype exists and no lectotype, neotype or epitype have been designated for this taxon.   
 Pileus 25–60(–80) mm in diameter, hemispherical or campanulate when young, expanding to convex or planoconvex, with or without a low, broad umbo; surface with distinct squamules at center, radially fibrillose or smooth towards margin; usually gray or gray-brown (7.5YR 4/1–4/2, 5/1–5/2; 10YR 5/1–5/4, 6/1–6/2), in some specimens with distinct blue-green tinges especially around center (Gley1 6/1, 7/1; Gley2 7/1, 8/1); dry or slightly viscid when moist; margin smooth or translucent-striate. Lamellae crowded, free, ventricose, up to 6 mm broad, white when young, later pink, with even, or white, flocculose edges. Stipe 20–70 × 3–7 mm, cylindrical, with slightly broad base; surface white with distinct blue-green tinges (Gley1 6/1, 7/1; Gley2 7/1, 8/1) especially near the base, smooth or with longitudinal brown or gray-brown fibrils, especially near base. Context in stipe and pileus white or slightly grayish. Smell usually strong and like leaves of Pelargonium, more rarely slightly raphanoid or indistinct. Taste similar to smell or indistinct. Spore print pink to pinkish brown.   
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Basidiospores [480, 20, 20] 7.0–10.0(–12.0) × (4.5–)5.0–7.5(–8.0) µm, avl × avw = 8.3–9.5 × 6.2–6.8 µm, Q = 1.17–1.55(–1.70), avQ = 1.32–1.48, ellipsoid or broadly ellipsoid, more rarely oblong, sometimes ovoid or slightly constricted in the middle. Basidia 17–35(–47) × 7–14 µm, tetrasterigmate, clavate, some with median constriction. Pleurocystidia metuloid, 60–100(–110) × 10–20(–25) µm, fusiform, narrowly fusiform or narrowly utriform, provided with 2–4(–5) apical hooks (usually entire, rarely bifid, and well-developed), with up to 4 µm thick wall, frequent all over lamellar faces. Intermediate cystidia similar to the pleurocystidia but smaller and/or with thinner walls, a few irregularly shaped, without distinct apical hooks and/or with rounded apices; without a predominant morphological type. Lamellar edge sterile. Cheilocystidia 25–70(–85) × 10–25 µm, predominantly clavate or narrowly clavate, hyaline, thin-walled, crowded, forming a well-developed strip. Pileipellis a cutis, with terminal elements 80–200(–270) × 6–18 µm, individual elements cylindrical, some strongly tapering towards apex, hyaline or filled with brown intracellular pigment, sometimes grayish or bluish in fresh specimens, with thin, smooth walls. Stipitipellis a cutis; hyphae 5–25 µm wide, cylindrical, hyaline or with brown intracellular pigment, with thin, smooth walls. Clamp-connections common and readily seen on pileipellis hyphae; also present and common in other parts of the basidiocarp.  
 Habit, habitat and phenology:—Solitary or subgregarious. Growing on decayed wood of hardwoods (e.g. Alnus, Eucalyptus, Fagus, Populus, Quercus,). In hardwood-dominated or mixed temperate forests, also in Eucalyptus plantations in Spain. May–November.   
 Distribution:— Eurasia: Widespread in western Europe and eastwards into Siberia.   
 HOLARCTIC SPECIES OF PLUTEUS SECTION PLUTEUS   
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 Observations:— The collection LE 289410 (Fig. 6a), made in the Novosibirsk Region (Russia), marks the easternmost confirmed occurrence of P. salicinus in Eurasia. All other collections in this species complex from the eastern parts of Eurasia and from North America have turned out to be different species.   
 Pluteus salicinus is relatively easy to recognize because of the combination of gray pileus with squamules at center; blue-green tinges in pileus and/or stipe; relatively large basidiospores; metuloids with well-developed hooks and presence of clamp-connections in pileipellis.   
 Additional collections examined: — RUSSIA. Northwestern Federal District: Leningrad Region, Kingiseppsky District, Kurgalsky Peninsula, Alnus glutinosa forest, on decayed wood of Alnus, 04 July 1997, O.V. Morozova s.n. LE 202301, nrITS KJ009755, tef1 KJ010023 (LE). Siberian Federal District: Novosibirsk Region, Novosibirsk District, Akademgorodok, mixed forest (Betula pendula, Pinus sylvestris), on decayed wood, 2008, I.A. Gorbunova s.n. LE 289410, nrITS KJ009758, tef1 KJ010025 (LE). Volga Federal District: Samara Region, Zhigulevsky Nature Reserve, Betula forest, on fallen trunk of deciduous tree, 11 June 2003, E.F. Malysheva s.n. LE 213033, nrITS KJ009753, tef1 KJ010022 (LE); ibid., broadleaf forest (Tilia cordata, Acer platanoides), on fallen trunk of deciduous tree, 25 July 2003, E.F. Malysheva s.n. LE 213034, nrITS KJ009756, tef1 KJ010028 (LE); ibid., broadleaf forest (Tilia cordata, Acer platanoides), on fallen trunk of deciduous tree, 26 July 2001, E.F. Malysheva s.n. LE 213064, nrITS KJ009754, tef1 KJ010024 (LE); ibid., broadleaf forest with Tilia cordata, on fallen trunk of deciduous tree, 25 July 2003, E.F. Malysheva s.n. LE 213023, nrITS KJ009757, tef1 KJ010027 (LE). SPAIN. Barcelona: La Floresta, on unidentified wood, 5 October 2002, A.M. Tarín s.n. SCM 4598 (SCM). Rupit, Pruit, on Fagus sylvatica stump, 1 June 1999, M. Tabarés s.n. SCM 4599 (SCM). Sta. Fe del Montseny, on Fagus sylvatica stump, 24 June 1987, A. Rocabruna s.n. SCM 120 (SCM); ibid., 19 July 1987, A. Rocabruna s.n. SCM 284 (SCM); ibid., 01 June 1988, M. Tabarés & A. Rocabruna s.n. SCM 1094 (SMC); ibid., 17 June 1995, A. Rocabruna s.n. SCM 2523 (SCM); ibid., 15 August 1995, A. Rocabruna s.n. SCM 2545 (SCM). Cádiz: Los Barrios, Arroyo del Tiradero, in forest of Quercus canariensis, Q. suber, Alnus glutinosa, on wood, 03 January 2004, A. González-Cruz & F. Prieto-García s.n. JA-CUSSTA 4098 (JA); Grazalema, Las Cumbres, on Quercus suber wood, 07 October 2001, A. Castro s.n. MA-Fungi 53681 (MA). Girona: Requesens, Castell, on Populus wood, 07 October 1995, A. Prunell s.n. LOU-Fungi 8264 (LOU). Riells, on wood of unidentified deciduous tree, 28 September 1996, A. Rocabruna s.n. SCM 3140 (SCM). Gipuzkoa: Tolosa, on wood of unidentified deciduous tree (Quercus rubra or Acer), 23 June 2001, P. Pasabán ARAN s.n (ARAN). Granada: Aldeire, Río Aldeire, in Populus forest, apparently terrestrial, 27 September 2003, A. Capilla s.n. JA-CUSSTA 4305 (JA). Huelva: Ribera del Múrtiga, La Nava, on Populus nigra wood, 18 October 1992, L. Romero de la Osa s.n. MA-Fungi 33470 (MA). Navarra: Bakaiku, Fagus forest, 07 November 2004, L. Garcia Bona s.n. MA 67874, nrITS HM562051, tef1 KJ010029 (MA). Oviedo: Lugones, mixed forest, on well-decayed hardwood log (probably Quercus or Castanea), 08 May 2005, L.A. Parra s.n. AJ 349, nrITS JN603199, tef1 KJ010026 (CUW). Somiedo, Veigas, on unidentified wood, 22. August 1997, E. Rubio-Domínguez s.n. MA-Fungi 38383 (MA).   
 Pluteus americanus (P. Banerjee & Sundb.) Justo, E.F. Malysheva & Minnis, comb. & stat. nov. Fig. 28 MycoBank 808736   
 Basionym: Pluteus salicinus var. americanus Banerjee & Sundberg, Mycotaxon 47: 393. 1993. Holotype:— UNITED STATES OF AMERICA. Michigan: Emmet Co., Pellston Hills, west of Pellston, 03 September 1957, on wood of Populus, A.H. Smith 57842, nrITS KJ009762, tef1 KJ010037 (MICH!).   
 Pileus 10–60 mm in diameter, hemispherical or campanulate when young, expanding to convex or plano-convex, with or without a low, broad umbo, sometimes slightly depressed at center; surface usually with distinct squamules at center, radially fibrillose or smooth towards margin; usually with predominant brown or pale brown colors (10YR 7/3–7/8, 8/3–8/8), darker and more gray-brown at center (10YR 5/1–5/3, 4/1–4/3), in some collections with distinct blue-green tinges especially center (Gley1 6/1, 7/1; Gley2 7/1, 8/1); dry or slightly viscid when moist, strongly hygrophanous; margin smooth or translucent-striate. Lamellae crowded, free, ventricose, up to 6 mm broad, white when young, later pink, with even, or white, flocculose edges. Stipe 15–65 × 3–6 mm, cylindrical, with slightly broad base; surface white, commonly with distinct blue-green tinges (Gley1 6/1, 7/1; Gley2 7/1, 8/1) especially near the base, sometimes all over the stipe, smooth or with longitudinal brown or gray-brown fibrils, especially near the base. Context in stipe and pileus white or slightly grayish. Smell usually strong and like leaves of Pelargonium, more rarely indistinct. Taste similar to smell or indistinct. Spore print pink to pinkish brown.   
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Basidiospores [110, 5, 4] 6.5–9.5(–11.0) × 4.5–7.0(–7.5) µm, avl × avw = 7.9–8.5 × 5.6–6.1 µm, Q = 1.29–1.59, avQ = 1.35–1.44, ellipsoid, more rarely broadly ellipsoid, sometimes ovoid or slightly constricted in the middle. Basidia 16–34 × 6–12 µm, tetrasterigmate, clavate, some with median constriction. Pleurocystidia metuloid, 50–93 × 12–24(–28) µm, fusiform, narrowly fusiform or narrowly utriform with 2–4 apical hooks (usually entire and well-developed, sometimes bifid), with up to 4 µm thick wall, frequent all over lamellar faces. Intermediate cystidia similar to the pleurocystidia but smaller and/or with thinner walls, a few irregularly shaped, without distinct apical hooks and/or with rounded apices; without a predominant morphological type. Lamellar edge sterile. Cheilocystidia 34–65(–70) × 12–22 µm, clavate, narrowly clavate or spheropedunculate, hyaline, thinwalled, crowded, forming a well-developed strip. Pileipellis a cutis, with terminal elements 80–194 × 10–22 µm, individual elements cylindrical, some strongly tapering towards apex, hyaline or filled with brown intracellular pigment, sometimes grayish or bluish in fresh specimens, with thin, smooth walls. Stipitipellis a cutis; hyphae 5–25 µm wide, cylindrical, hyaline or with brown intracellular pigment, with thin, smooth walls. Clamp-connections common and readily seen on pileipellis hyphae; also present and common in other parts of the basidiocarp.  
 Habit, habitat and phenology:—Solitary or gregarious. Growing on decayed hardwoods (Fraxinus, Populus). In hardwood-dominated or mixed, temperate or transitional forests. August–September.   
 Distribution:— Eurasia. Known only from the Russian Far East (Primorsky Territory). North America. Known with certainty from Illinois, Michigan and New York, probably more widespread in the Eastern parts. Not recorded from western North America.   
 Observations:— Banerjee & Sundberg (1993) described Pluteus salicinus var. americanus as different from the type variety based on the hygrophanous pileus, the translucent-striate pileus margin and pleurocystidia with “compound ornamentation” (i.e. with bifid hooks). Based on our observations, margin striation and the proportion of pleurocystidia with bifid hooks are not really different from what is found in Pluteus salicinus. P. americanus has a pileus with more predominantly brown tinges that is strongly hygrophanous while P. salicinus has a more grayish pileus that is less markedly hygrophanous but both characters intergrade to some extent. Geographical distribution is probably the best character to tell both species apart, with Pluteus salicinus confined to Eurasia and Pluteus americanus in North American and the Russian Far East. Many of the North American records of Pluteus salicinus probably correspond to Pluteus americanus, but some may correspond to other taxa in this group (e.g. P. oreibatus, P. saupei).   
 The separation of both taxa is not supported in the nrITS phylogenies, however they appear as separate species in the tef1 and combined analyses, with statistical support in the former (Fig. 6).   
 Additional collections examined: — RUSSIA. Far East Federal District: Primorsky Territory, Ussuriisky Nature Reserve, Peishula Reserve Field Station, valley of Suvorovka River, floodplain forest (Chosenia, Salix, Corylus), on decayed wood of deciduous tree, 15 August 2011, E.F. Malysheva s.n. LE 289369, nrITS KJ009759, tef1 KJ010034 (LE). UNITED STATES OF AMERICA. Illinois: Cook Co., Elk Grove Village, Busse Woods, mixed forest, on Fraxinus wood, 09 September 2013, A. Houghtby MO145100, nrITS KJ009785, tef1 KJ010038 (CUW). Michigan: Emmet Co., French Farm, 25 September 2009, M. Keirle SF2-BPI 882765, nrITS HM562174, tef1 KJ010035 (BPI). New York: Essex Co., Adirondack Ecological Center, Huntington Wildlife Forest, mixed forest, on decayed wood, 18 August 2012, A. Justo 591, nrITS KJ009760 (CUW); ibid., A. Justo 596, nrITS KJ009761, tef1 KJ010036 (CUW).   
 Pluteus sepiicolor E.F. Malysheva, sp. nov. Fig. 29   
MycoBank 808733  
 Diagnosis:—Differs from other species in the P. salicinus complex (P. salicinus, P. americanus, P. oreibatus) by the combination of deep brown pileus, metuloid pleurocystidia with predominant bifid apical hooks, the presence of clampconnections in pileipellis and growth on conifers.   
 Holotype:— RUSSIA. Far East Federal District: Primorsky Territory, Sikhote - Alinsky Nature Biosphere Reserve, vicinities of Kabany Reserve Field Station, Picea - Abies forest with isolated Alnus and Betula, on mossy wood, 24 August 2011, A.E. Kovalenko s.n. LE 289365, nrITS KJ009765, tef1 KJ010030 (LE!).   
 Etymology:— sepiicolor refers to color of pileus (sepia, deep brown).   
Pileus 40–60 mm in diameter, nearly hemispherical or obtusely campanulate when young, expanding to convex or plano-convex, with a low, broad umbo; surface smooth or innately radially fibrillose, at center squamulose with dark (almost black) slender squamules; deep brown or sepia (7.5YR 4/3–4/6, 3/3–3/4); dry or slightly viscid when moist, hygrophanous; translucent-striate at margin. Lamellae crowded, free, slightly ventricose, up to 5 mm broad,  
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white-cream when young, later pink, with concolorous edges. Stipe 50–70 × 4–6 mm, cylindrical, slightly broadened towards base (up to 7–8 mm); surface white or yellowish in the upper part, grayish brown in the lower part; longitudinally fibrillose, with blackish brown fibrils. Context in stipe and pileus white or slightly grayish yellow. Smell indistinct. Taste not recorded. Spore print not recorded.  
 HOLARCTIC SPECIES OF PLUTEUS SECTION PLUTEUS   
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Basidiospores [60/3/2] 7.8–8.6 (–9.0) × 5.0–6.2 (6.5) µm, avl × avw = 8.0–8.3 × 5.4–5.8 µm, Q = 1.29–1.60, avQ = 1.38–1.47, ellipsoid to oblong, some ovoid, occasionally with medial constriction. Basidia 20–30 × 5.5–10 µm, tetrasterigmate, narrowly to broadly clavate. Pleurocystidia metuloid, 40–90 × 13–25 µm, fusiform, narrowly fusiform or narrowly utriform with 2–4(–5) apical hooks (commonly bifid, but entire hooks also present), hyaline, thick-walled (up to 2.7–3.0 µm). Intermediate cystidia similar to the pleurocystidia but slightly smaller and/or with thinner walls. Lamellar edge sterile. Cheilocystidia 40–70 × 8–20 µm, clavate, narrowly clavate or narrowly utriform, some with slightly elongated apices, hyaline, thin-walled, crowded, forming a well-developed strip. Pileipellis a cutis, with repent and slightly ascending hyphae; terminal elements 80–120 × 10–25 µm, individual elements narrowly fusiform, filled with yellow-brown intracellular pigment, thin-walled. Stipitipellis a cutis; hyphae 7–20 µm wide, cylindrical, hyaline or with brown intracellular pigment, with thin, smooth walls. Clamp-connections present on pileipellis hyphae but not at every septum, also present and common in other parts of the basidiocarp.  
 Habit, habitat and phenology:—Solitary. Growing on decayed or mossy wood of conifers. In mixed or conifer forests in mountain area. August.   
 Distribution:— Eurasia. Known only from the Russian Far East (Primorsky Territory).   
 Observations:— Pluteus sepiicolor can be distinguished from P. salicinus and P. americanus by the growth on conifers and the dark brown colors of the pileus. P. oreibatus also grows on conifers but has differently shaped pleuro and cheilocystidia. Both nrITS and tef1 phylogenies recover P. sepiicolor as a separate species in the salicinus clade.   
 Pluteus nigropallescens Singer (1961a: 116) can also have dark colors in the pileus but it differs from P. sepiicolor in the pleurocystidia with entire hooks and the terrestrial habitat. This species is only known from Venezuela (Singer 1961a). Pluteus velutinornatus can also present pleurocystidia with bifid hooks, but it has a more markedly fibrillose-squamulose pileus, usually wrinkled at center, and pigmented lamellar edges (Stevenson 1962; Horak 2008). This species is only known from New Zealand.   
 Additional collection examined: — RUSSIA. Far East Federal District: Primorsky Territory, Sikhote - Alinsky Nature Biosphere Reserve, vicinities of Kabany Reserve Field Station, conifer forest, on decayed wood, 24 August 2011, N. V . Psurtseva s.n. LE 289366, nrITS KJ009766, tef1 KJ010031 (LE).   
 Pluteus oreibatus Justo, sp. nov. Fig. 30   
MycoBank 808734  
 Diagnosis:—Differs from other species in the P. salicinus complex (P. salicinus, P. americanus., P. sepiicolor) by the combination of pleurocystidia with poorly developed hooks, cheilocystidia cylindrical or lageniform, and the growth on conifer wood.   
 Holotype:— UNITED STATES OF AMERICA. North Carolina: Haywood Co., Great Smoky Mountains National Park, Cataloochee Valley, Rough Fork Trail, 09 October 2010, on fallen conifer wood, E. C. Vellinga 4183, nrITS KJ009763, tef1 KJ010033 (TENN!).   
 Etymology:— oreibatus comes from the Greek term “ορειβατηϛ” which roughly translates to “mountain ranging” or “to walk on mountains”. It is given to this species for its distribution in the Smoky Mountains and the Adirondacks.   
Pileus 20–40 mm in diameter, convex or plano-convex, with a low, broad umbo; surface smooth or with some squamules and fibrils around center; dark brown or gray-brown (7.5YR 3/2–3/4, 4/1–4/6); dry or slightly viscid when moist; margin smooth or only slightly translucent-striate. Lamellae crowded, free, ventricose, up to 5 mm broad, white when young, later pink, with even, or white, flocculose edges. Stipe 20–50 × 3–5 mm, cylindrical, with equal or slightly broadened base; surface white, smooth or with longitudinal brown or gray-brown fibrils, especially near the base. Context in stipe and pileus white. Smell sweetly raphanoid or indistinct. Taste not recorded. Spore print not recorded.  
Basidiospores [40, 2, 2] (7.0–)7.5–9.0 × 5.0–7.0 µm, avl × avw = 7.9–8.3 × 5.5–5.9 µm, Q = 1.29–1.60, avQ = 1.42–1.45, ellipsoid, more rarely broadly ellipsoid or oblong, sometimes ovoid or slightly constricted in the middle. Basidia 16–34 × 6–12 µm, tetrasterigmate, clavate, some with median constriction. Pleurocystidia metuloid, 55–75(–85) × 12–20 µm, fusiform, narrowly fusiform or narrowly utriform with 2–3 apical hooks (not welldeveloped, usually rounded and not very prominent), some with truncate apex and/or without apical hooks, with up to 2 µm thick wall, frequent all over lamellar faces. Intermediate cystidia occurring in two morphological types (i) similar to the pleurocystidia with thinner walls; (ii) cylindrical or lageniform (similar to cheilocystidia) with slightly thickened walls and occurring in clusters; either type can be predominant. Lamellar edge sterile. Cheilocystidia 36–80 × 9–15 µm, cylindrical, lageniform, narrowly utriform or narrowly clavate, hyaline, thinwalled, crowded, forming a well-developed strip. Pileipellis a cutis, with terminal elements 80–132 × 8–15 µm,  
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individual elements cylindrical, some strongly tapering towards apex, hyaline or filled with brown intracellular pigment, with thin, smooth walls. Stipitipellis a cutis; hyphae 5–22 µm wide, cylindrical, hyaline or with brown intracellular pigment, with thin, smooth walls. Clamp-connections common and readily seen on the pileipellis hyphae at all septa or nearly so; also present and common in other parts of the basidiocarp.  
 Habit, habitat and phenology:—Solitary. Growing on decayed wood of conifers. In mixed forests in mountain areas. August–October.   
 Distribution:— North America. Known only from the Great Smoky Mountains National Park (North Carolina) and the Adirondack mountains (New York).   
 Observations:— Pluteus oreibatus can be separated from P. americanus by the growth on conifers and the shape of the cheilocystidia. Pluteus saupei also has lageniform cheilocystidia but it lacks the cylindrical or narrowly clavate ones that are present in P. oreibatus.   
 Pluteus amphicystis (Singer 1958: 213) also has pleurocystidia without distinct apical hooks but it differs from P. oreibatus in the yellow coloration of the pileus, the smaller basidiospores (up to 6.3 µm long), the smaller cheilocystidia (up to 28 µm long) and the lack of clamp-connections. This taxon has ben reported from Bolivia (Singer 1958), Martinique (Pegler 1983), India (Pradeep et al. 2002) and Mexico (Rodríguez 2014).   
 Additional collection examined: — UNITED STATES OF AMERICA. New York: Essex Co., Adirondack Ecological Center, Huntington Wildlife Forest, mixed forest, on decayed conifer wood, 17 August 2012, D. Floudas s.n. AJ 600 , nrITS KJ009764, tef1 KJ010032 (CUW).   
 Pluteus saupei Justo & Minnis in Justo et al. (2011a: 475). Fig. 31   
 Holotype:— UNITED STATES OF AMERICA. Illinois: Champaign Co., Urbana, Brownfield Woods, 05 August 1980, on decaying log, S. G. Saupe 230, nrITS HM 562113 (ILLS!).   
Pileus 10–35 mm in diameter, convex or plano-convex, with shallow depression at center; surface innately radially fibrillose, with blackish, spinulose squamules at center, gray to gray-brown, bruised regions become blue, with olive green tinges in older specimens; margin translucent-striate in older specimens. Lamellae crowded, free, ventricose, approx. 5 mm broad, pink, with slightly paler edges. Stipe 10–50 × 3–5 mm, cylindrical, broadened towards base; surface white, with some longitudinal fibrils near the base, turning blue when bruised, with olive green tinges in older specimens. Context color not recorded, probably whitish. Smell and taste not recorded. Spore print pinkish brown.  
Basidiospores [30, 1, 1] 6.5–9.0(–10.0) × 5.0–6.5(–7.0) µm, avl × avw = 7.7 × 5.8 µm, Q = 1.15–1.60(–1.70), avQ = 1.33, (broadly) ellipsoid, rarely oblong. Basidia 17.5–26 × 7.5–10 µm, tetrasterigmate, rarely bisterigmate,  
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clavate, oblong or ellipsoid, some with median constriction. Pleurocystidia metuloid, 70–85 × 17–22 µm, fusiform or narrowly utriform, with 2–4 hooks at apices, but hooks usually poorly developed, hyaline, with up to 2 µm thick walls, frequent all over lamellar faces. Lamellar edge sterile. Cheilocystidia 45–85 × 9.5–19.5 µm, mostly lageniform with elongated apices, some fusiform or ovoid, hyaline, thin-walled, crowded, forming a welldeveloped strip. Pileipellis a cutis, with terminal elements 80–135 × 10–16 µm; individual elements cylindrical, some strongly tapering towards apex, mostly filled with brown intracellular pigment, with thin, smooth walls. Stipitipellis a cutis; hyphae 5–15 µm wide, cylindrical, hyaline or with intracellular brown pigment, with thin, smooth walls. Clamp-connections present in all tissues, more abundant at the base of cheilocystidia and on pileipellis.  
 Habit, habitat and phenology:—Solitary. Growing on decayed wood. In mixed mesophytic upland forest. August   
 Distribution:— North America: Known only from central Illinois (USA).   
 Observations:—Nothing can be added to the original description (Justo et al. 2011) reproduced above. The predominantly lageniform cheilocystidia with elongated apices are the most distinctive morphological feature of Pluteus saupei.   
 VI. atromarginatusclade. Fig. 7   
Species growing or conifer wood. Lamellar edges pigmented (brown, dark brown) over their entire length. Clampconnections common and easy to spot on pileipellis hyphae.  
 Pluteus atromarginatus (Singer) Kühner (1935: 51). Fig. 32   
 Basionym: Pluteus cervinus var. atromarginatus Singer (1925: 40). The holotype collection has been destroyed (Singer 1956; Banerjee & Sundberg 1995) and no other kind of type has been designated.   
 Synonym: Pluteus tricuspidatus Velenovský (1939: 143). To the best of our knowledge, no holotype exists and no other material has been designated as any kind of type.   
 Synonym: Pluteus cervinus var. nigrofloccosus Schulz (1912: 102); Pluteus nigrofloccosus (Schulz) J. Favre (1948: 104). To the best of our knowledge, no holotype exists and no other material has been designated as any kind of type.   
 Synonym: Pluteus pseudoroberti Moser & Stangl (1963: 39), emend. Vellinga (in Vellinga & Schreurs 1985: 340). Holotype:— GERMANY. Baden-Wurttemberg: Aalen, Spitwald, 30 August 1951, rotting wood, MM Moser 51/100, nrITS KJ009769, tef1 KJ010017 (M!).   
 Synonym: Pluteus atropungens Smith & Bartelli, (1965: 65). Holotype:— UNITED STATES OF AMERICA. Michigan: Marquette Co., Marquette, 20 October 1959, on sawdust, I. Bartelli, A. H. Smith 62033, nrITS HM 562059, tef1 KJ010013 (MICH!).   
 Synonym: Pluteus laricinus Banerjee & Sundberg (1993: 392). Holotype:— UNITED STATES OF AMERICA. Michigan: Oakland Co., Proud Lake Recreation Area, 30 October 1951, on rotten Larix log, A.H. Smith 38888, nrITS KJ009772 (MICH!).   
Pileus 25–100(–120) mm in diameter, hemispherical or campanulate when young, expanding to convex or planoconvex, with or without a low, broad umbo; strongly radially fibrillose all over or only around center, usually with distinct squamules around center; brown (7.5YR 5/4–5/8, 4/3–4/8, 3/3–3/4), or gray (Gley2 4/1, 5/1), usually darker at center; dry or slightly viscid when moist; margin smooth or translucent-striate. Lamellae crowded, free, ventricose, up to 10 mm broad, white when young, later pink, with distinct dark brown edges for the whole length of the lamella, very rarely only colored in the part near the margin of pileus. Stipe 40–120 × 4–11 mm, cylindrical, with slightly broad base; surface white, or whitish gray, commonly covered with dense gray-brown fibrils all over, more rarely only near the base. Context in stipe and pileus white or slightly grayish. Smell sweet, fungoid or indistinct. Taste similar to smell. Spore print pink to pinkish brown.  
Basidiospores [300, 15, 15] (5.5–)6.0–8.5(–9.0) × 4.0–6.0(–7.0) µm, avl × avw = 6.8–7.5 × 4.8–5.2(–5.9) µm, Q = (1.00–)1.30–1.70, avQ = (1.24–)1.32–1.52, ellipsoid to oblong, more rarely broadly ellipsoid, very rarely globose or subglobose, sometimes ovoid or slightly constricted in the middle. Basidia 16–35 × 6–12 µm, tetrasterigmate, rarely bisterigmate or monosterigmate, clavate, some with median constriction. Pleurocystidia metuloid, 60–110 × 10–20(–25) µm, fusiform, narrowly fusiform or narrowly utriform, some with a bifurcated apex, provided with 2–5 apical hooks (usually entire and well-developed), rarely without apical hooks, with up to 5 µm thick wall, frequent all over lamellar faces. Intermediate cystidia similar to the pleurocystidia but smaller and/ or with thinner walls, a few irregularly shaped, without distinct apical hooks and/or with rounded apices; without a predominant morphological type; some with intracellular brown pigment. Lamellar edge sterile. Cheilocystidia  
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25–110(–140) × 10–30 µm, mostly narrowly clavate or clavate, some narrowly utriform or spheropedunculate, the majority filled with intracellular brown pigment but hyaline ones also occur, thin-walled, crowded, forming a welldeveloped strip. Pileipellis a cutis, with terminal elements (40–)70–190(–210) × 7–24(–30) µm; individual elements cylindrical, some strongly tapering towards apex, with brown intracellular pigment, with thin, smooth walls. Stipitipellis a cutis; hyphae 5–20 µm wide, cylindrical, hyaline or with brown intracellular pigment, with thin, smooth walls. Clamp-connections common and readily seen on pileipellis hyphae; also present and common in other parts of the basidiocarp.  
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 Habit, habitat and phenology:—Solitary or subgregarious. Growing on decayed wood of conifers (e.g. Picea, Pinus, Larix), very rarely on sawdust or angiosperm wood (e.g. Populus). In conifer-dominated or mixed forests and plantations, in temperate and mountainous areas. July–November (–February in Mediterranean areas).   
 Distribution:— Eurasia. Widespread in western Europe and eastwards into Siberia. North America. Widespread, known from the eastern and western parts.   
 Observations:— Pluteus atromarginatus is one of the most distinct taxa in the section, characterized by the relatively large basidiocarps, fibrillose-squamose pileus, dark brown lamellar edges, presence of clampconnections, and very thick-walled pleurocystidia.   
 Molecular data from the type collections of P. pseudoroberti, P. atropungens and P. laricinus show that these species are synonyms of P. atromarginatus. All three represent unusual morphological variants of P. atromarginatus.   
 The presence of clamp-connections was not mentioned in the original description of P. pseudoroberti but the revision of the type by E.C. Vellinga did reveal numerous clamp-connections on the pileipellis, therefore the taxonomic concept of this species did radically change (Vellinga & Schreurs 1985). Most of the cheilocystidia in the collection are hyaline, and only a few have intracellular brown pigment (Bonnard 1995; pers. obs.) so a relation with P. atromarginatus was not suspected. The nrITS sequences in GenBank under the name P. pseudoroberti correspond to P. hongoi (JN021083) and P. pellitus (JF908600, JF908603).   
 Pluteus atropungens was described as a separate species (Smith & Bartelli 1965) because of the smooth metuloids without hooks. The type collection does have predominantly non-hooked metuloids, a phenomenon also observed in some collections from Spain (Justo & Castro 2007a). The type also has a wider than usual variation in size and shape of basidiospores; all exceptional values (in parentheses) for these two characters in the above description come from the type study of P. atropungens.   
 Pluteus laricinus was described by Banerjee & Sundberg (1993) based on a collection by Alexander Smith with grayish lamellar edges but only near the margin of the pileus. All other characters fit well our concept of P. atromarginatus.   
 Additional collections examined: — RUSSIA. Siberian Federal District: Novosibirsk Region, Novosibirsk District, Akademgorodok, mixed, poorly lit eutrophic planted forest (Pinus sylvestris, Betula pendula) ca. 40 years old with a lot of dead trees, on decayed wood of Pinus, rotten half-buried trunk, 07 July 2011, T.M. Bulyonkova s.n. LE 289425, nrITS KJ009770, tef1 KJ010012 (LE); ibid., relic Ob terrace Pinus sylvestris forest, on Pinus stump, 21 September 2011, Vlad Labetsky s.n. LE 289417, nrITS KJ009771, tef1 KJ010011 (LE). SPAIN. A Coruña: Camariñas, Pinus forest, on decayed wood of Pinus, 19 October 2008, A. Justo & GMG AJ75, nrITS HM562061, tef1 KJ010015 (LOU); ibid., J. Rodriguez & GMG s.n. AJ76, nrITS HM562040, tef1 KJ010016 (LOU). Corcubión, Finisterre, Pinus forest, 3 October 1983, L. Freire & M. Pérez-Froiz s.n. LOU-Fungi 6267 (LOU). Santiago de Compostela, on Pinus pinaster wood, 19 January 1986, L. Freire & M. Castro s.n. LOU-Fungi 2709 (LOU); ibid., 26 October1988, A. Zaera & L. Rodríguez s.n. LOU-Fungi 4437 (LOU). Barcelona: Dosrius, Pinus pinaster forest, 9 January 1993, M. Tabarés & al. s.n. SCM 2078 (SCM). Castellón: Fredes, Pinar Plá, on Pinus sylvestris wood, 17 October 2001, P. Daniels s.n. MA-Fungi 52174 (MA). Pina del Montalgrao, Umbría de Santa Bárbara, on Pinus sylvestris stump, 17 October 1996, F. Tejedor PT 108 (LOU). Vistabella del Maestrat, Sanahuja, on Pinus sylvestris stump, 26 October 1997, F. Tejedor PT 235 (LOU). Gipukzoa: Ezkio Itsaso, on Pinus radiata wood, 30 August 1999, Z.E. Aranzadi s.n. ARAN 5037215. Girona: Nevà (Ripollès), on unidentified conifer wood, September 1996, M. Tabarés s.n. SCM 3128 (SCM). Jaén: Orcera, Los Negros, in Pinus nigra & Pinus halepensis forest, on wood, 25 October 2003, J. de Dios Reyes García s.n. JA-CUSSTA 4071 (JA). Navarra: Alsasua, on Pinus sylvestris stump, 23 September1995, P. Pasabán s.n. ARAN s.n. (ARAN). Pontevedra: As Neves, on Pinus pinaster stump, 10 February 2002, J. Rodríguez-Vázquez s.n. LOU-Fungi 16667 (LOU). Cangas, Cabo Home, in Pinus forest in sand dunes, 18 October 1993, J. Rodríguez-Vázquez & L. Freire s.n. LOU-Fungi 7093 (LOU). Carretera de Porriño a Gondomar, 25 November 1982, F.D. Calonge s.n. MA-Fungi 4503 (MA). Sta. María de Oia, 15 December 2001, X. Varela s.n. LOU-Fungi 17382 (LOU). Vigo, Campus As Lagoas-Marcosende, on Pinus stump, 23 September 2002, A. Justo LOU-Fungi 18235 (LOU); Vigo, Parque Forestal de Beade, on Pinus stump, 20 October 2003, P. Lorenzo & A. Justo s.n. LOU-Fungi 18232 (LOU). Vigo, Saians, 6 December 2001, X. Varela s.n. LOU-Fungi 17309 (LOU). Vigo, Zamáns, on Pinus pinaster stump, 9 November 1980, C. Castro s.n. LOU- Fungi 2710 (LOU). Soria: Duruelo de la Sierra, in Pinus sylvestris forest, 15 September 1992, F. Martínez-Peña s.n. VALON 941 (VALON). Pinar Grande, on Pinus pinaster stump, 10 September 1992, F. Martínez s.n. VALON 959 (VALON). San Leonardo de Yagüe, on Pinus sylvestris stump, 5 June 1995, S.A. Romanillos s.n. VALON 1244 (VALON). Tardelcuende, on Pinus pinaster wood, 25 October 2001, Ibon s.n. VALON 1909 (VALON). UNITED   
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 STATES OF AMERICA. California: Alameda Co., Berkeley, Santa Fe Ave., on decayed wood of Pinus, 22 November 2011, N.H. Nguyen s.n. UC 1998538, nrITS JX857451 (UC). Marin Co., Point Reyes National Seashore, at edge of recently burned coastal scrubland with scattered Pinus, on stump, 28 January 2006, E.C. Vellinga s.n. UC 1859503, nrITS KF306035 (UC). Tuolumne Co., Yosemite National Park, Along HWY 41, at Rail Creek, mixed conifer forest with Pinus ponderosa, Pinus lambertiana, Calocedrus sp., and Quercus kelloggii, on conifer wood, 29 October 2011, N.H. Nguyen s.n. UC 1860913, nrITS JX857464, tef1 KJ460251 (UC); ibid., pulloff on West Side of HWY 41, mixed conifer forest with Pinus ponderosa, Pinus lambertiana, Calocedrus sp., and Quercus kelloggii, 29 October 2011, G. Cobian s.n. UC 1860914, nrITS JX857465, (UC). Oregon: Jefferson Co., Suttle Lake area, near Sisters Deschutes National Forest, 07 October 1987, W.J. Sundberg 3657, nrITS HM562083 (ILLS). Tennessee: Knox Co., Knoxville, 21 September 2009, J.M. Birkebak 09210901, tef1 KJ010014 (TENN).   
 Pluteus atrofibrillosus Vellinga & Justo, sp. nov. Fig. 33   
MycoBank 808735  
 Diagnosis:—Differs from Pluteus atromarginatus in the more loosely arranged fibrils and squamules on the pileus, the slightly smaller basidiospores and the pleurocystidia predominantly with 2 apical hooks.   
 Holotype:— UNITED STATES OF AMERICA. Tennessee: Sevier Co., Gatlinburg, near Little Creek, 07 October 2010, on conifer wood, E. C. Vellinga 4153a, nrITS KJ009774, tef1 KJ010020 (TENN!).   
 Etymology: atrofibrillosus is from the Latin words “ater” (dark) and “fibrillosus” (with fibers) referring to the pileus covered with dark fibrils.   
Pileus 25–55 mm in diameter, hemispherical or campanulate when young, expanding to convex or plano-convex, with or without a low, broad umbo, strongly radially fibrillose all over, fibrils usually group to form squamules around center, sometimes with small squamules all over; brown (7.5YR 6/6–6/8, 5/6–5/8), darker at center (7.5YR 3/3–3/4); dry or slightly viscid when moist; margin smooth or translucently striate. Lamellae crowded, free, ventricose, up to 5 mm broad, white when young, later pink, with distinct dark brown edges over the whole length of the lamella. Stipe 30–70 × 3–6 mm, cylindrical, with slightly broad base; surface white, or whitish gray, smooth or with longitudinal gray-brown fibrils, especially near the base. Context in stipe and pileus white. Smell not recorded. Taste not recorded. Spore print not recorded.  
Basidiospores [90, 3, 3] 5.5–7.5 × 4.0–5.5(–6.0) µm, avl × avw = 6.5–6.8 × 4.5–5.1 µm, Q = 1.19–1.60, avQ = 1.30–1.46, ellipsoid or broadly ellipsoid, very rarely oblong, sometimes ovoid or slightly constricted in the middle. Basidia 16–29 × 6–9 µm, tetrasterigmate, some with median constriction. Pleurocystidia metuloid, 45–75 × 11–23 µm, fusiform, narrowly fusiform or narrowly utriform, some with a bifurcated apex, the majority provided with 2 apical hooks (usually entire and well-developed), more rarely with 3–4 or none, with up to 3 µm thick wall, frequent all over lamellar faces. Intermediate cystidia similar to the pleurocystidia but smaller and/or with thinner walls, a few irregularly shaped, without distinct apical hooks and/or with rounded apices; the non-hooked morphotype predominant, or without a predominant morphological type; some with intracellular brown pigment. Lamellar edge sterile. Cheilocystidia 41–65 × 9–22 µm, mostly narrowly clavate or narrowly utriform, the majority filled with intracellular brown pigment but hyaline ones also occur, thin-walled, crowded, forming a welldeveloped strip. Pileipellis a cutis, with terminal elements 68–143 × 9–16 µm; individual elements cylindrical, some strongly tapering towards apex, with brown intracellular pigment, with thin, smooth walls. Stipitipellis a cutis; hyphae 5–25 µm wide, cylindrical, hyaline or with brown intracellular pigment, with thin, smooth walls. Clamp-connections common and readily seen on pileipellis hyphae; also present and common in other parts of the basidiocarp.  
 Habit, habitat and phenology:—Solitary or subgregarious. Growing on decayed wood of conifers. In mixed temperate forests. October.   
 Distribution:— North America. Only known from three places in the Great Smoky Mountains National Park (Tennessee and North Carolina, USA)   
 Observations:— Pluteus atrofibrillosus is very similar to Pluteus atromarginatus but the fibrils and squamules on the pileus appear more loosely arranged. The slightly smaller basidiospores (on average 6.5–6.8 × 4.5–5.1 µm) and the pleurocystidia also smaller (45–75 × 11–23 µm) and mostly with only 2 hooks at apex may be helpful to separate both species on microscopical grounds, but this should be checked in future collections of P. atrofibrillosus.   
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 Pluteus similis has a darker pileus and pleurocystidia that are longer (up to 90 µm long) and provided with 3–6 apical hooks (Horak 2008). Pluteus microspermus and Pluteus concentricus share with P. atrofibrillosus the pigmented lamellar edges but they lack clamp-connections (Horak 2008). All these species are endemic to New Zealand (Horak 2008). The South American species Pluteus squamosopunctus has darker colors in the pileus, which is covered with pyramidal squamules, and pleurocystidia provided with 4–6 apical hooks (Horak 1964).   
 Additional collections examined: — UNITED STATES OF AMERICA. Tennessee: Cocke Co., Cosby, near Low Gap Trail, on conifer wood, 10 October 2009, E. C . Vellinga 4207, nrITS KJ009773, tef1 KJ010018 (TENN). Sevier Co., Gatlinburg, Cherokee Orchad Road, before Rainbow Falls Trailhead, on wood, 10 October 2009, B . Looney s.n. ECV 4169, nrITS KJ009775, tef1 KJ010019 (TENN).   
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description: Published as part of Justo, Alfredo, Malysheva, Ekaterina, Bulyonkova, Tatiana, Vellinga, Else C., Cobian, Gerry, Nguyen, Nhu, Minnis, Andrew M. & Hibbett, David S., 2014, Molecular phylogeny and phylogeography of Holarctic species of Pluteus section Pluteus (Agaricales: Pluteaceae), with description of twelve new species, pp. 1-85 in Phytotaxa 180 (1) on pages 60-73, DOI: 10.11646/phytotaxa.180.1.1, http://zenodo.org/record/10090263