Guyanaporus albipodus T.W. Henkel & Husbands, in Henkel et al., Mycologia 108(1): 164 (2016)
Etymology: Albus (Latin adj. A) = white and -podus (Greek adj. A) = footed, in reference to the stipe with copious white basal mycelium.
Diagnosis: Pileus grayish brown, dry, glabrous macroscopically, low tomentulose under hand lens, minutely areolate toward margin, trama white to pale yellow, bluing slowly on exposure. Hymenophore tubulose, shallowly depressed and sublamellate at stipe, grayish yellow, bluing slowly with pressure, immature pores nearly stuffed, with age subisodiametric, then finely ovate and angular, 2–3 per mm. Stipe equal, concolorous, pale yellow at extreme apex, longitudinally striate over lower three-quarters, reticulate over upper one fourth, base densely white tomentose, trama white, unchanging, solid. Basidiospores brownish olive in deposit, smooth, ovoid-ellipsoidal, mean Q 5 1.68, inamyloid. Basidia narrowly to broadly clavate, strongly tapering toward base, sterigmata two or four. Pleurocystidia ventricose-rostrate to sublanceolate. Cheilo‐ cystidia absent. Hymenophoral trama parallel to slightly divergent (phylloporoid), mediostratum barely distinct, concolorous. Pileipellis a trichodermium with polymorphic terminal elements, these cylindrical, clavate, ventricose, or ventricose-rostrate. Clamp connections absent. NH4OH and KOH unreactive on all surfaces.
Pileus 34–75 mm broad, (7–)15–21 mm tall, convex to planate to strongly upturned with age, grayish brown (6F4–6F5, 7F3–7F4), glabrous macroscopically, under hand lens a dense contiguous low tomentum, with age minutely areolate over marginal one-third revealing whitish ground, dry to submoist; margin slightly incurved and undulating when young, otherwise entire; trama 1–2 mm thick at margin, 6–11 mm above tubes, 9–10 mm above stipe, white to pale yellow (2A2), bluing slightly and slowly with exposure, solid. Odor mild to somewhat rank, farinaceous; flavor mild, indistinctive. Tubes 1–3 mm long at margin, 2–5 mm centrally, 2–4 mm at stipe, of slightly irregular heights when mature, shallowly and narrowly depressed around stipe and there slightly sublamellate and with short, decurrent teeth descending into upper stipe reticulum, initially pale grayish yellow (2B4–3B4), darker concolorous (3B5–3B6) when mature, bluing instantly upon exposure; edges concolorous, bluing slowly and moderately with pressure, this eventually browning; pores initially convoluted, substuffed, then subisodiametric to ovate and subangular, 2–3 per mm. Stipe (47–) 60–97 6 7–20 mm centrally, equal but broadening to 14–25 mm at base due to dense basal mycelium, grayish brown (6F3–6F4), pale yellow (3A2–3A3) at extreme apex, longitudinally striate over lower three-quarters with lighter ground between striations; striations merging upward into distinct reticulum over upper one-quarter; basal mycelium a dense white tomentum, occasionally yellowish orange with age, surrounding the basal one-fifth of the stipe; trama white, unchanging, yellowing around larval channels, solid.
Basidiospores olive to brownish olive (4D4–5D4, 4D7–4E7) in medium deposit, (6–) 7–8(–9) x 4–5 μm, Q range 1.4–1.9 (mean Q = 1.68), ovoid-ellipsoidal with suprahilar depression, pale olivaceous in H2O, concolorous but lighter in KOH, inamyloid, smooth, mostly 1–2 guttulate; hilar appendage 0.3– 0.4 mm long; wall 0.4–0.5 μm thick; surface under SEM smooth. Basidia (20–)25–37.1(–45) x (6–)7.5– 10(–12) μm, narrowly to occasionally broadly clavate, strongly tapering toward base, devoid of refractive contents or with varying degrees of olivaceous brown granulation and globules in H2O, paler in KOH; sterigmata 3–6 μm long, two or four per basidium. Pleurocystidia infrequent, (27–)37–57(–79) x (5–)7.5–10(–14) μm, narrowly ventricose-rostrate to occasionally sublanceolate, projecting (10–)12.5–27 μm above the hymenial palisade, devoid of refractive contents, hyaline in H2O and KOH. Cheilocystidia absent. Hymenophoral trama phylloporoid, parallel to slightly divergent, non-gelatinizing, in mass light yellow-gray in H2O, paler in KOH; individual hyphae somewhat inflated, 5–10(–12.5) μm wide, hyaline to faint gray in H2O and KOH; mediostratum barely distinct, concolorous, 10–39.5 μm wide; conductive hyphae rare, opaque and hyaline. Pileipellis a trichodermial palisade with terminal elements projecting at slightly unequal lengths, in mass pale gray or light orangish yellow in H2O, paler in KOH; individual hyphae faint yellow in KOH; terminal elements (25–)37–66.5(–87) x (5–) 8.5–15(–20) μm, cylindrical, clavate, ventricose, or ventricose-rostrate; subpellis hyphae anticlinally arranged, close-septate, variably inflated. Pileus trama interwoven; hyphae (3.5–) 5–10(–12.5) μm wide, hyaline in H2O and KOH, somewhat inflating, devoid of contents or minutely granulose. Stipitipellis a trichodermial palisade, in mass olivaceous orange in H2O, olivaceous gray in KOH; sterile terminal cells cylindrical, clavate, mucronate, ventricose, or ventricose-rostrate, 22–39.5 x (5–) 7.5–10 μm, hymenidermous in grooves between apical stipe reticulations with numerous two- or foursterigmate basidia, these apparently nonsporulating, 34.5–37 x 7.5– 10 μm, narrowly clavate with long tapered base; contents variously granulose-guttulate. Stipe trama interwoven, in mass orangish gray in H2O, paler yellow-gray in KOH; individual hyphae 3.5–10 μm wide, somewhat inflating, irregularly branching, hyaline; conductive hyphae rare, opaque, faintly yellow. Clamp connections absent. Macro chemical reactions: 10% NH4OH and 3% KOH not reactive on all surfaces.
Habit, habitat and distribution: Solitary to scattered on the humic mat of the forest floor under D. corymbosa; also found in stands of P. dipterocarpacea and D. jenmanii; known from the type locality in the Upper Potaro River Basin and , 25 km to the west in the Upper Mazaruni Basin.
Index Fungorum number: IF 811837
Figure 1: Maximum likelihood phylogram (−ln 36456.292067) based on 28S ribosomal DNA and RPB1 sequences depictin phylogenetic relationships of the new Guyanese bolete taxa Binderoboletus segoi, Guyanaporus albipodus, Singerocomus inundabilis and Singerocomus rubriflavus within the Boletaceae. Support values above the nodes are maximum likelihood bootstrap support values. Nodes with bootstrap support values , 75 are not shown. Clades with multiple species from the same genus are collapsed into triangles for visual simplification as is a clade of outgroup taxa from other suborders or families of Boletales.