Agaricus globocystidiatus Drewinski & M.A.Neves, 2017

Drewinski, Mariana De Paula, Junior, Nelson Menolli & Neves, Maria Alice, 2017, Agaricus globocystidiatus: a new neotropical species with pleurocystidia in Agaricus subg. Minoriopsis, Phytotaxa 314 (1), pp. 64-72 : 68-69

Agaricus globocystidiatus Drewinski & M.A.Neves sp. nov. ( Figs. 2 , 3 )

Mycobank: MB821296

Diagnosis:—Similar to Agaricus pleurocystidiatus by the presence of pleurocystidia, but differing in the pileus surface covered by concentrically arranged purple scales, regular pileus margin, and stipe with brown scales and slightly yellowish on some parts when exposed.

Etymology:— glob- (L.) refers to the main shape of the pleurocystidia and cystidium (L.) refers to the presence of pleurocystidia, a rare morphological character in this genus.

Holotype:— BRAZIL. Santa Catarina: Florianópolis, Universidade Federal de Santa Catarina, near to the Department of Botany , 10 December 2015, M.P. Drewinski MPD29 ( FLOR61594 ).

Description: —Pileus 30–122 mm diam., at first parabolic, then conical truncated to convex and finally expanding to plano-convex, slightly depressed, covered by concentrically arranged purple (oac527) scales on beige (oac780) background, darker at center with concentrated scales that are scattered towards the margin, margin regular. Pileus context approx. 5mm thick at center and 1mm at margin, whitish or slightly yellowish in some parts when exposed, fleshy. Lamellae free, white at first, then pinkish and finally brown when mature, margin regular, crowded, with lamellulae. Stipe 102–120 × 9–20 mm, central, tapering at base, fistulose, beige pearly (oac767), smooth above annulus, with brown scales below, changing to yellow in some parts including the context of the base. Annulus superous, pendant, membranous, floccose on lower surface, whitish.

Basidiospores [200/10/8] (4.0–)5.0–6.2(–7.5) × (3.7–)5.0 μm, [Q= 1.25–1.66; Q m = 1.42; L m =5.3μm; W m =4.2μm], broadly ellipsoid to ellipsoid, dark brown, smooth, thick-walled, apiculus conspicuous, without a germ pore. Basidia (16.2–)21–37(–40) × 6.2–10.0(–11.2) μm, narrowly utriform to clavate, hyaline, smooth, 4-spored. Pleurocystidia (25–)26–43 × (16.2–)18.7–23 μm, globose, subglobose, ovoid to broadly clavate, hyaline, smooth, thin-walled. Cheilocystidia (11.2–)13.7–45(–47) × (7.5–)10–21(–23) μm, clavate, subglobose to obovoid, hyaline, thin-walled, usually covering all the lamellae edge. Lamellar trama regular, with abundant oleiferous hyphae, up to 6.5(–8.7) μm diam. Pileipellis a cutis composed of cylindrical and thin- to rather thick-walled hyphae, (3.7–)5.0–11.2μm diam., branched, with purple internal plasmatic pigments. Pileus context composed of cylindrical and thin-walled hyphae, (5.0–)6.2–12.5 μm diam., with abundant oleiferous hyphae. Stipitipellis a cutis composed of cylindrical and thin-walled hyphae, 5.0–10.0 μm diam., sometimes inflated. Macrochemical reactions yellow in 3% KOH (positive), yellow in 10% NaOH (positive). Schaffer’s reaction was unclear, but the pileus turned purple with citric acid. Odor sweet almond.

Habit, habitat and distribution:—solitary to gregarious, terrestrial, growing on grass in urban areas and areas of the Atlantic Forest domain; Brazil, Santa Catarina and Paraná states.

Specimens examined:— BRAZIL. Santa Catarina: Florianópolis, at the University Campus near the Botany Department , 30 July 2015, M.P. Drewinski MPD02 ( FLOR61586 – Paratype) ; 05 October 2015, M.P. Drewinski MPD03 (SP466715– Paratype) ; 07 October 2015, M.P. Drewinski MPD04 ; 16 March 2016, M.P. Drewinski MPD128 ( FLOR61612 – Paratype) ; 09 February 2017, M.P. Drewinski MPD145 ( FLOR61620 – Paratype) ; Parque Ecológico do Córrego Grande , 11 February 2016, E.Copini EC31 ( FLOR61583 ) ; Cacupé , Tim Brightwell MPD19 ( FLOR61582 ) ; Paraná: Guarapuava, Parque Municipal das Araucárias, 12 January 2016, M.P. Drewinski MPD71 ( FLOR61599 ) .

Notes:—The presence of pleurocystidia is a rare morphological character in Agaricus . Although those pleurocystidia are large and stand out from the other structures in the hymenium, they are not abundant and may go unnoticed if the material is not carefully studied ( Heinemann 1980). Agaricus globocystidiatus is similar to A. pleurocystidiatus Heinem. (1980:12) , from Singapore, mainly due to the presence of pleurocystidia and because of the similar annulus that is described as membranous, pendant, white and with flakes on the lower side ( Heinemann 1980). However, A. pleurocystidiatus differs by the following: the pileus surface, which has dark brown scales on a light brown background; the pileus margin, which is appendiculate; and the fibrillose light brown stipe. Furthermore, A. pleurocystidiatus changes to reddish brown when cut and is known only from Singapore ( Heinemann 1980).

Agaricus sinodeliciosus Z.R. Wang & R.L. Zhao (2015:192) from China also has pleurocystidia ( Wang et al. 2015). However, A. sinodeliciosus differs by its semi-hypogeous habit (growing buried in sandy soil), pileus surface covered with light brown or buff brown squamules on a dirty background, involute margin, smooth or fibrillose white stipe that becomes reddish brown when bruised, negative Schäffer and KOH reactions, inferior annulus forming a broad sheath, and context that turns reddish brown when cut ( Wang et al. 2015).

Agaricus martinicensis Pegler (1983:446) is the type species of Agaricus subg. Minoriopsis . Agaricus globocystidiatus is similar to A. martinicensis by the presence of cheilocystidia, by the purplish brown contents of the pileipellis, both species have the stipe covered with squamules below the annulus and a thin, membranous, pendent, white annulus that has floccose remnants of the universal veil at the lower surface. Agaricus globocystidiatus differs from A. martinicensis by the larger and beige pileus with purple scales and the presence of pleurocystidia.

The basidiomata of Agaricus globocystidiatus collected in Brazil share some characters attributed to Agaricus subg. Minoriopsis ( Chen et al. 2017) , including an annulus that is superous, a positive reaction to KOH, and the presence of clavate, subglobose to obovoid cheilocystidia. The other two species in the genus known to have pleurocystidia, A. pleurocystidiatus and A. sinodeliciosus , change to reddish brown upon cutting and belong to Agaricus subg. Pseudochitonia sect. Sanguinolenti Schaeff. & Moll. and sect. Bivelares (Kauffman) L.A. Parra, respectively ( Heinemann 1980; Wang et al. 2015).

Agaricus globocystidiatus is a new species in Agaricus subg. Minoriopsis supported by morphological and molecular data. Although it is necessary to revise the morphology of the collection MATA816 (JF727870) to confirm the presence of pleurocystidia, our molecular results indicate that it is most likely A. globocystidiatus , which suggests a possible neotropical distribution for the new species here described. All sequences in A. globocystidiatus clade are 98.8–100% identical, with MATA816 presenting levels of sequence divergence between 1.2% and 0.1% compared to Brazilian sequences (MPD02 and MPD19, respectively). This work increases the knowledge of taxa within this subgenus and of Agaricus species that occur in America, which is important to better understand the phylogenetic relationships and the biogeographic patterns in the genus.

Figures

FIGURE 2. Microcharacters of Agaricus globocystidiatus FLOR 61594 (MPD29–Holotype). a. Pileipellis; b. Basidia; c. Cheilocystidia; d. Pleurocystidia; e. Basidiospores. Scale bars: 5μm. Drawings by M.P.Drewinski.

FIGURE 3. Agaricus globocystidiatus a–b. Basidiomata; a. FLOR61620 (MPD145); b. FLOR 61594 (MPD29–Holotype); c. Pileus surface FLOR 61599 (MPD71); d. Stipe with details of the scales and annulus with floccose lower surface FLOR61620 (MPD145); e. Pleurocystidia FLOR 61594 (MPD29–Holotype); f. Pleurocystidia (MPD04). Photos by M.P.Drewinski.