Agaricus guzmanii Linda J. Chen & G. Mata, 2019

Chen, Jie, Callac, Philippe, Llarena-Hernández, Régulo Carlos & Mata, Gerardo, 2019, Two species of Agaricus subg. Minoriopsis from Mexico, Phytotaxa 404 (3), pp. 91-101 : 95-96

Agaricus guzmanii Linda J. Chen & G. Mata sp. nov. ( Figs. 2 , 3 )

Mycobank: MB 829915 Facesoffungi number: FoF 05821

Etymology:—This specific epithet honors the excellent mycologist Gastón Guzmán for his great contribution to Mycology.

Macroscopic description:—Pileus 4.5–7 cm diam., at first hemispherical then plano-convex, finally plane at maturity, covered by brownish fibrillose squamules or scales on whitish background, with an entirely brown center. Surface dull and dry. Margin slightly exceeding the lamellae. Lamellae free, straight, intercalated with numerous lamellulae, white for a long time, staining pink when handled, finally brown at maturity. Stipe 7–10 × 0.5–0.8 cm (up to 1.5 cm at base), cylindrical and bulbous at base, fistulose, with an annulus in its upper third, above annulus smooth, below annulus fibrillose, white, faintly yellowing when bruised. Annulus superous, double, white, membranous, upper surface smooth, lower surface covered with whitish to brownish floccose or scales. Context white, firm, no discoloration when cut. Odor of bitter almonds.

Microscopic description:—Basidiospores (4.1–)4.2–4.9(–5.3) × 2.8–3.3 (–3.4) μm, (x = 4.6 × 3.1 μm, Q = 1.3– 1.64, Qm = 1.43, n = 80), ellipsoid, smooth, brown, without apical pore. Basidia 12–16 × 5.5–6 μm, tetrasporic, clavate, hyaline, smooth. Cheilocystidia abundant, hyaline, simple or septate at the base, terminal elements versiform, most frequently clavate and sometimes slightly narrowed in the middle, pyriform, ovoid or cylindrical, sometimes fusiform, utriform, or lageniform, 10–29 × 4–11 μm; anteterminal elements, when present, more or less cylindrical of 6–15(– 20.5) × 5–8.5 μm. Pleurocystidia not observed. Lower surface of the annulus composed of hyaline hyphae, cylindrical, not or slightly narrowed at septa, 3–10 μm wide. Inflated elements not observed. Pileipellis a cutis composed of cylindrical and thin-walled hyphae of 3.5–7 μm wide, hyaline or with brownish membranous pigment, sometimes slightly constricted at the septa. Clamp connections not observed.

Macrochemical reactions:—Schäffer’s reaction positive, orangish red. KOH reaction positive, yellow.

Habit and habitat:—gregarious or scattered on leaf litter.

Material examined:— MEXICO, Xalapa , Instituto de Ecología, Campus 1, 2 October 2018, N.M. Montiel, LD201807 ; Xalapa , Instituto de Ecología, Campus 1, 18 October 2018, J. Chen, LD201811 Holotypus ; Xalapa , Instituto de Ecología, Campus 1, 18 October 2018, J. Chen, LD201812 ; Xalapa , Instituto de Ecología, Campus 1, 18 October 2018, J. Chen, LD201813 ; Xalapa , Veracruzana University, in front of the faculty of biology, 19 October 2018, C. Ortega Sánchez, LD201814 .

Notes:— Agaricus guzmanii is characterized by its medium-sized sporocarps, a pileus surface covered with brownish fibrillose squamules or scales, double annulus with lower surface covered with whitish to brownish floccose or scales.

According to our phylogenetic results, the new species is closely related to a putative species (F 1779 in Fig. 1 ). By comparing with the original notes of J.P. Fiard (via LIP Herbarium), the collection F1779 differs in having larger spores (4.5–5.25 × 4–4.25 μm) and pleurocystidia.

Agaricus guzmanii is also macroscopically similar to A. luteofibrillosus M.Q. He, Linda J. Chen & R.L. Zhao (2016: 126) of A. subg. Minores and A. subtilipes Thongklang, Linda J. Chen, Callac & K.D. Hyde (216: 243) of A. subg. Flavoagaricus in the pileus covered with brownish squamules. However, A. luteofibrillosus differs in its simple annulus and brownish fibrils on its stipe surface ( Chen et al. 2017). Agaricus subtilipes differs in white floccose squamules on its stipe surface and catenulate cheilocystidia ( Thongklang et al. 2016).

Figures

FIGURE 1. Maximum likelihood phylogram of Agaricus subg. Minoriopsis and A. subg. Minores resulting from analysis of ITS sequence data. The bootstrap support values greater than 50% are indicated, and branches with Bayesian posterior probabilities greater than 0.8 are in bold. Species sampled from Mexico are in red. T = Type specimen.

FIGURE 2. Macroscopic characteristics of A. guzmanii. a–c. Basidiomata. a–b. (LD201811, holotype); c. (LD201813).

FIGURE 3. Microscopic characteristics of A. guzmanii. a–c. (LD201811, holotype). a. Basidia; b. Spores; c. Cheilocystidia. Bars = 5 μm.