Agaricus subrufescens Peck, Ann. Rep.

Parra, Luis A., Angelini, Claudio, Ortiz-Santana, Beatriz, Mata, Gerardo, Billette, Christophe, Rojo, Carlos, Chen, Jie & Callac, Philippe, 2018, The genus Agaricus in the Caribbean. Nine new taxa mostly based on collections from the Dominican Republic, Phytotaxa 345 (3), pp. 219-271 : 232-235

Agaricus subrufescens Peck, Ann. Rep. New York State Mus. 46: 105. 1893. ( Figs. 4–5 )

Note: For the numerous synonyms of A. subrufescens see Kerrigan (2005), Parra (2013), Thongklang et al. (2016) and Chen et al. (2016a).

Macroscopic description: Pileus 4.4–9.0 cm diam., at first hemispherical or conical, then hemispherical or trapezoid, finally plano-convex, sometimes depressed at the disc, other times broadly mammilate with umbilicate center, background whitish covered by fine hazelnut brown squamules, scales more appressed at center, which is darker. Surface fibrillose, dull and dry. Margin slightly exceeding the lamellae even in mature basidiomata. Lamellae free, crowded, straight, intercalated with numerous lamellulae, at first pinkish white, then pale pink for a long time, finally dark brown in mature basidiomata, with the edge even and concolorous. Stipe 4–9 × 0.70–1.31 cm, cylindrical, sometimes curved at the base, slightly enlarged to bulbous at base, fistulose, with an annulus in its upper third; above annulus at first white then pink, smooth, below annulus white, pruinose when young, frequently covered by a white floccosity particularly towards the base; slightly yellowing on handling. At times with a single thick rhizomorph or with abundant fine mycelial strands at the base. Annulus superous, double, white, up to 3.75 cm broad, fragile and fine, upper surface smooth, lower surface covered by concolorous floccose to floccose-lanose squamules. Context in pileus and stipe dense, when cut at first white then yellowing, soon ochre salmon, with strong odor of anise.

Microscopic description: Spores 4.94–5.32–5.70[–6] × 3.10–3.72–4.22 μm, Q=1.30–1.44–1.67, ellipsoid, smooth, brown, without apical pore. Basidia 13–20 × 6–7.5 μm, tetrasporic, clavate or slightly truncated at the apex, sterigmata up to 3 μm long. Cheilocystidia hyaline or with a brown diffuse pigment, frequently catenulate, terminal element globose, usually spherical, ovoid, or ellipsoid, 4–13 × 4–9 μm, the anteterminal elements also globose or more or less cylindrical with rounded ends, 3–11 × 5–9 μm. Pleurocystidia not observed. Lower surface of the annulus consisting of two types of hyphae, some cylindrical very narrowed at the septa, composed of elongated elements of 6–13 μm wide, rare; other abundant generally consisting of globose, spherical or slightly ovoid or inflated elements, narrowed at the septa, readily disarticulating, up to 23 μm wide. Pileipellis a cutis, with a transition to a trichoderm at the discal and peridiscal squamulose areas, hyphae cylindrical, the wider the more constricted at septa, 2–10 μm diam., terminal elements abundant, 4–7 μm wide, gradually to abruptly attenuated towards the apex, which is more or less rounded. Clamp-connections not observed.

Macrochemical reactions: Schäffer’s reaction positive, color reddish orange. KOH reaction difficult to read because of the orange yellow color of the exsiccatum.

Habit, habitat, occurrence and distribution: Gregarious, sometimes in rows of numerous basidiomata, in lowland broadleaf forests, particularly prevalent on leaf litter of Terminalia (tropical almond trees). Very common. Cosmopolitan.

Note: This species is characterized by its large size and robustness, the whitish pileus more or less covered by ochraceous squamules, the very broad and particularly subtle annulus with is lower surface covered by concolorous floccose to floccose-lanose squamules, by the context quickly turning ochre salmon and the strong odor of anise.

Material examined: DOMINICAN REPUBLIC, Puerto Plata, Sosúa, Perla Marina , 23 November 2011, JBSD123801 ( LAPAM12 ), Puerto Plata, Sosúa, Perla Marina, 6 December 2011, JBSD126504 ( LAPAM13 ) ; Puerto Plata, Sosúa, Puerto Chiquito , 20 November 2011, JBSD123800 ( LAPAM11 ) ; Puerto Plata, Sosúa , cemetery, 16 December 2013, JBSD126481 ( LAPAM37 ) .

Taxonomic comments: We want to emphasize that although the spore sizes of the Dominican collections are slightly smaller (4.94–5.32–5.70[–6] × 3.10–3.72–4.22 μm) than those measured for A. subrufescens in North and South America, Europe and China ( Kerrigan, 2005; Parra, 2013; Gui et al. 2015), they are very similar to the measurements of collections from Thailand ( Wisitrassameewong et al. 2012), particularly to collection MFLU 100065 (4.5–6 × 3–4 μm) and to the African collection Gooss.-Font.283 ([4.9–]5.1–5.6–6.0[–6.2] × [3.2–]3.3–3.6–3.9[–4.0] μm), type of A. bambusae Beeli (1928: 93) var. bambusae now considered a synonym of A. subrufescens ( Thongklang et al. 2016) .

Additional comments: An unusual intraspecific variability is known in this cosmopolitan species. Chen et al. (2016a) noted that the ITS can be classified into three different types based on nine informative polymorphic positions that are reported in the Table 5. ITS sequences of collections from the Americas and Europe are of types A / A, B / B or A / B, while those from samples collected from Hawaii, Thailand, China, and more recently from Iran ( Mahdizadeh et al. 2017) are of type C. The European sample CA 487 unusually bears the three types of ITS A, B and C. We used three sequences obtained from PCR-clones of CA 487 by Chen et al. (2016a) as haplotypes of reference A, B, and C, respectively. Based on the alignment of eight sequences used in the phylogenetic analysis, the Table 5 reveals that the two Dominican samples LAPAM 13 and LAPAM 37 are of type A / A like the sample F 2285 from Martinique while the sample LAPAM 12 is of type B / B. The sequence of the sample LAPAM 11 agrees with the presence of the two types A and B. The type A / B is particularly frequent among the field collections, and most cultivars have it. The representation of this intraspecific diversity in the phylogenetic tree is not reliable since the heteromorphisms and the indels at crucial informative positions are not taken in consideration.

The ITS sequence data perfectly support not only the presence of A. subrufescens but also the presence of the three ITS types ( A / A, B / B and A / B) in the Caribbean Islands (Hispaniola and Martinique). This includes the sample F 2285 from Martinique collected and identified as A. fiardii by J.- P. Fiard who also collected the specimen Fiard 353 that Pegler (1983) designated as the holotype of A. fiardii . Although F 2285 undoubtedly belongs A. subrufescens , the question of whether or not Fiard 353 is conspecific with A. subrufescens warrants further studies before any attempt to synonymize the two species. This precaution is particularly necessary in this case, because we suspect the presence of a distinct entity closely related to A. subrufescens in the Caribbean, based on four collections from the Dominican Republic. We do not describe these four samples in this study, because that would require a comprehensive treatment, including the comparison of sequences on a wider geographic scale, which is beyond the scope of this study.

Figures

FIGURE 4. Macroscopic characters of A. subrufescens. A–J. Basidiomata. A, E. (JBSD123800); B–C, G, I. (JBSD123801); D, F, H. (JBSD126481); J. (JBSD126504). Photos by C. Angelini.

FIGURE 5. Microscopic characters of A. subrufescens A–H. In ammoniacal Congo red. A–C, F–H. (JBSD123801); D. (JBSD123800); E. (JBSD126481).A–C. Cheilocystidia. D. Basidia. E. Spores. F. Hyphae of the lower surface of the annulus. G–H. Pileipellis hyphae. H terminal elements. Photos by L.A. Parra.