Cortinarius altissimus Harrower & T.W. Henkel

Harrower, Emma, Bougher, Neale L., Winterbottom, Caitlin, Henkel, Terry W., Horak, Egon & Matheny, P. Brandon, 2015, New species in CortinariussectionCortinarius (Agaricales) from the Americas and Australasia, MycoKeys 11, pp. 1-21 : 8

Taxon classification Fungi Agaricales Cortinariaceae

Cortinarius altissimus Harrower & T.W. Henkel sp. nov. Fig. 1, 2g, 3c, 4c

Diagnosis.

Similar to Cortinarius kerrii Singer & I.J.M.Araujo but differs by its larger basidia and less frequent, much larger pleurocystidia. Unique molecular synapomorphies at pos. 46, 108, 156, 212, 216, 259, 260, 261, 262, 264 (ITS1), 440, 503, 506, 532, 545, 554, 583, 617 (ITS2) are present in our alignment.

Type.

GUYANA. Region 8 Potaro-Siparuni: Pakaraima Mountains, Upper Potaro River Basin, vicinity of Potaro base camp at 5°18'04"N; 59°54'40"W, 710 m alt., on lateritic soils; 2 km southeast of base camp near Dicymbe plot 1, on humic mat of forest floor under Dicymbe corymbosa , May 25 2001, T.W.Henkel 8211 (holotype: BRG 41220; isotype TENN 069829, HSU G1168)

Etymology.

Refers to the exceptionally tall basidiomata of the species, due to the long stipe.

Description.

Pileus 24-56 (-87) mm wide, 17-29 mm tall, convex to plano-convex with a low, broad umbo with age, surface dry, erect tomentulose-squamulose throughout, especially over disc, under hand lens squamules subpyramidal and subacuminate, 0.5 mm tall, dark violet (16F7-16F8, 17F7-17F8), lighter concolorous (16E8) near margin, red in KOH; margin entire, broadly undulating with age. Lamellae subclose, shallowly adnexed with short decurrent tooth, subthick, 2 mm broad at margin, 8-10 mm centrally, 7 mm at stipe, concolorous (16F5-17F5), browning with basidiospore development; edges concolorous, hispid under hand lens; lamellulae usually 3 (2 short at 1-3 mm, 1 long at 6-21 mm), occasionally 5, rarely 7. Stipe 132 –220(– 263) mm long, (2-) 5-11 mm thick at apex, (3-) 7-17 mm thick at center, (7-) 12-24 mm thick at base, subequal, tapering gradually from base to apex, concolorous (16F5-16F6) or slightly lighter concolorous (16D7-16E7, 17D7-17E7) over lower 4/5, apex slightly more greyish violet (15D6-15D7), finely longitudinally striate throughout, with appressed longitudinal fibrils visible under hand lens, cartilaginous, snapping easily, red with KOH. Partial veil cortinate, rather scant, concolorous, minimally retained as scattered, rust-brown fibrils on upper stipe and occasionally pileus margin. Basal mycelium a pale purple (16B3-16B4) matted tomentum. Pileus context subsolid, off white to light purple (17A4-17B4), unchanging, 0.5-1 mm thick at margin, 1-1.5 mm centrally, 6 mm above stipe. Stipe context cartilaginous and concolorous in outer rind, core hollow and off-white, reddening instantly with KOH. Smell mild, slightly fruity to musty. Taste minimal, indistinct.

Basidiospores dark orange–brown (7E7-7E8) in heavy deposit, 10-16 × 8-11 (-13) µm, means = 12-14 × 9.5-11 µm, Q = (1.0-) 1.10-1.44 (-1.56), Q means = 1.18-1.33 (70 spores, 5 specimens), ellipsoid to amygdaloid, verrucose, plage present under SEM. Basidia 4-spored, clavate, (40-) 50-60 (-65) × (8-) 9-15 (-16) µm. Cheilocystidia scattered to abundant, ventricose-rostrate to lageniform, opaque greyish or brown in KOH, (60-) 70-90 (-100) µm × (10-) 20-30 (-40) µm. Pleurocystidia infrequent, ventricose to ventricose–rostrate, grey or rarely brown in KOH, (60-) 70-110 (-125) × (10-) 25-40 (-45) µm. Pileipellis a trichoderm, organized into discrete, suberect fascicles; hyphae (10-) 15-30 (-35) µm wide, (225-) 270-500 (-550) µm high, light brown in KOH, multiseptate; terminal cells undifferentiated, rounded at apex, or occasionally subclavate. Clamp connections present.

Ecology and distribution.

Solitary to scattered on humic mat of forest floor in forests dominated by Dicymbe corymbosa ( Caesalpinioideae) on lateritic soils; also occurring in forests dominated by Dicymbe altsonii , Aldina insignis ( Papilionoideae), and Pakaraimaea dipterocarpacea ( Dipterocarpaceae ) and Dicymbe jenmanii on white sand soils; known only from the Upper Potaro and Upper Mazaruni River Basins in the Pakaraima Mountains of Guyana, in the central Guiana Shield.

Other specimens examined.

Guyana, Region 8 Potaro-Siparuni: Pakaraima Mountains, Upper Potaro River Basin, within a 15 km radius of Potaro base camp at 5°18'04"N; 59°54'40"W, 710 m alt., on lateritic soils; 1 km SE of Potaro base camp on Benny’s Ridge, (Dicymbe corymbosa), 7 July 2003, T.W.Henkel 8539 (BRG; HSU G1169; TENN 069831). ~15 km E of Potaro base in vicinity of Tadang base camp, (Dicymbe altsonii, Aldina insignis), 30 Dec 2009, T.W.Henkel 9180 (BRG; HSU G1170; TENN 069830). 200 m southwest of Tadang base camp (Dicymbe corymbosa, Dicymbe altsonii, Aldina insignis), 6 June 2013, T.W.Henkel 9752 (BRG; HSU G1171). Region 7 Mazaruni-Cuyuni: Pakaraima Mountains, Upper Mazaruni River Basin, within 1 km radius of base camp at 5°26'21"N, 60°04'43"W, ~800 m alt., on white sand soils; 1 km SW of base camp in monodominant stand of Pakaraimaea dipterocarpacea, 25 Dec 2010, T.W.Henkel 9543 (BRG; HSU G1172). Pakaraima Mountains, Upper Mazaruni River Basin, within 1 km radius of base camp at 5°26'21"N, 60°04'43"W, ~800 m alt., on white sand soils; 1 km SW of base camp in monodominant stand of Pakaraimaea dipterocarpacea, 5 June 2012, T.W.Henkel 9690 (BRG; HSU G1173).

Discussion.

Cortinarius altissimus was treated as ' Cortinarius sp. SA1' in Harrower et al. (2015). The species has an exceptionally long stipe compared to the width of its pileus, and overall one of the longest stipe lengths recorded in the genus. The size of its basidiospores overlaps with that of Cortinarius kerrii , which is known from Amazonia. However, the size of the basidia and cystidia are twice that of Cortinarius kerrii . Additionally, pleurocystidia are infrequent in Cortinarius altissimus sp. nov. whereas they are abundant in Cortinarius kerrii . Cortinarius altissimus sp. nov. is a prominent member of the ECM fungal assemblage associated with Dicymbe monodominant forests in Guyana. In a long-term Dicymbe corymbosa plot study of Henkel et al. (2012), basidiomata of Cortinarius altissimus sp. nov. occurred in 5.2% of 630 quadrats sampled during the May–July rainy seasons over seven years. Phylogenetically (Fig. 1), Cortinarius altissimus sp. nov. is most closely related to other taxa of the Cortinarius violaceus group that also occur in the Americas.