Guyanagarika aurantia Sánchez-García, T.W. Henkel & Aime, in Sánchez-García et al., Fungal Biology 120(12): 1544 (2016)
Etymology: from the Latin aurantia ¼ orange-coloured, in reference to the uniform colour of the basidioma.
Diagnosis: Morphological characteristics of the genus and similar to G. pakaraimensis and G. anomala, but forming a distinct species-level clade supported by multiple loci data (ITS, LSU, rpb1, and rpb2). The ITS sequence is 82-90 % similar to other species of Guyanagarika, unique molecular synapomorphies at positions 31, 33, 34, 82, 109, 129, 133, 134 (ITS1); 357, 359, 423, 466 (ITS2). The LSU sequence is 92e96 % similar to other species of Guyanagarika, unique molecular synapomorphies at positions 176, 415, 427, 436, 440, 430, 442, 443, 460, 461, 467, 489, 558, 608, 609, 616, 685, 690, 697, 778, 779. The rpb2 sequence is 98-99 % similar to other species of Guyanagarika, unique molecular synapomorphies at positions 7, 857, 927.
Pileus 30-60 mm broad, 15-32 mm tall, convex to sub-conic to plano-convex with prominent umbo 6e13 mm tall with age, orange throughout (5A8-6B3), darker orange (6B8-6C6) over disc when young, hygrophanous somewhat to lighter yellowish orange (4A6-4A7) with age, otherwise uniformly concolourous, margin incurved and sub-crenulate to crenulate when young, and broadly undulate at maturity, edge sub-crenate; surface glabrous to minutely tomentose especially over disc, under hand lens a regular, low, sub-erect to erect pile of fibrillose elements more concentrated over disc, on mature specimens near margin erect elements reduced, nearly minutely granulose-pruinose; sub-dry to moist; trama off-white to pale cream (4A3-4A4), orange-concolourous under pileipellis, 0.5 mm at margin, 2 mm over lamellae, and 9 mm over stipe/umbo, unchanging. Lamellae sub-thick to thick, sub-distant, adnate-adnexed when young, sinuate at maturity, cream to light orange (4A5-4A6-4A7), brittle, unchanging; edges concolourous, smooth, irregularly slightly eroded in places; one to three lamellulae 1-7 (-10) mm long. Stipe 45-105 (-180) 6-11 (-15) mm, equal to subequal or tapering evenly and slightly from apex to base, usually light orange (4A5-4A6), rarely creamish orange (4A3-4A4), sometimes lightening to nearly white over basal one-fifth, glabrous to finely longitudinally striate macroscopically, under hand lens with a fine, dense, and longitudinal mat with occasional minute projecting elements; trama offwhite, faintly cream near stipitipellis, fibrous, solid, snapping easily and cleanly, cartilaginous; basal mycelium an off-white mat subtended by thin to thick white hyphal chords. Odour none, or fungoid when cut to slightly soapy-chemical. Taste none to slightly farinaceous.
Basidiospores 7.2-8.5 x 4.4-5.5 μm (mean 7.96 x 5.12 μm), hyaline, smooth, ellipsoid, Q range = 1.4-1.8, Q mean = 1.59, inamyloid, acyanophilic, usually containing 2-4 guttules. Basidia 38-52 x 4.4-7 μm, clavate, 4-sterigmate, occasionally 2- sterigmate, hyaline. Edge of the lamellae sterile due to the presence of short, clavate, thin-walled cells resembling basidioles and rarely protruding elements. Hymenial cystidia absent. Hymenophoral trama regular to slightly interwoven. Pileipellis a cutis made up of interwoven hyphae, orangeochraceous in mass with intracellular pigments; cells 48-80 x 6-9 μm, with ascending terminal cells; subpellis consisting of interwoven hyphae. Stipitipellis a cutis; cells 61-100 x 8- 10 μm with ellipsoid to cylindrical terminal elements. Clamp connections and thromboplerous hyphae present in all tissues.
Habit, habitat, and distribution: Solitary to scattered on humic mat on sandy soils under the ECM trees Pakaraimaea dipterocarpacea and Dicymbe jenmanii in the Upper Mazaruni River Basin of Guyana; also found under Dicymbe corymbosa in the Upper Potaro and Upper Ireng River Basins of Guyana.
Figure 1. Maximum likelihood phylogeny (LSU, SSU, rpb1, rpb2) of the suborder Tricholomatineae. Bootstrap values ≥ 70 are shown above branches and Bayesian posterior probabilities ≥ 0.90 are shown below branches.
Figure 2. Maximum likelihood phylogeny (LSU, SSU, rpb1, rpb2, ITS) of the family Catathelasmataceae. Bootstrap values ≥ 70 are shown above branches and Bayesian posterior probabilities ≥ 0.90 are shown below branches.