Hymenagaricus splendidissimus (Watling) Kun L. Yang, Jia Y. Lin & Zhu L. Yang

Yang, Kun L., Lin, Jia Y., Li, Guang-Mei, Liu, Zhen-Chao, Hosen, Md. Iqbal & Yang, Zhu L., 2024, Heinemannomyces, Hymenagaricus and Xanthagaricus revisited (Basidiomycota, Agaricaceae), Phytotaxa 659 (2), pp. 112-164 : 125-127

Hymenagaricus splendidissimus (Watling) Kun L. Yang, Jia Y. Lin & Zhu L. Yang , comb. nov. ( Fig. 3 )

≡ Heinemannomyces splendidissimus Watling, Belgian Journal of Botany 131(2): 135 (1999)

Registration identifier:— FN571946

Description:— Basidiomata small to medium-sized. Pileus 39–62 mm in diameter, convex, plano-convex to plano-concave; background ceramic white (#FEFEFA); squamules flaky, floccose to fibrous at center, becoming entirely floccose to fibrous towards margin, meat brown (#D7B19D), sandal brown (#BA8B70) to dark pepper red (#764840), becoming lighter towards margin; margin with appendices concolorous with the squamules on the pileus; context ceramic white (#FEFEFA) when fresh, turning rust orange (#D79A65) to sandal brown (#BA8B70) after damaged. Lamellae free, crowded, ceramic white (#FEFEFA), dirty blue (#A4BAC0) to cadet blue (#A9B5C3), sometimes mottled, with an entire to slightly serrate edge; lamellulae abundant. Stipe 60–84 mm long, 3–5 mm thick, cylindrical to subcylindrical, slightly curved; background ceramic white (#FEFEFA) to dull thatch yellow (#D3D3B7); squamules floccose to fibrous, usually more abundant below the annulus, concolorous with the squamules on the pileus; context ceramic white (#FEFEFA) when fresh, turning rust orange (#D79A65) to sandal brown (#BA8B70) after damaged; base without specialized tomenta. Annulus superior, easily broken and fugacious, concolorous with the squamules on the pileus. Odor fungal. Taste fungal.

Basidiospores [40/3/3] 5.5–6.5 [6.04 ± 0.26, 6.00] × 3–4 [3.56 ± 0.30, 3.50] µm, Q = 1.50–2.00 [1.71 ± 0.14, 1.71], obovoid, ellipsoid to oblong, slightly thick-walled, smooth under both LM and SEM, tinged dull blush red (#CDA19C), eggplant pink (#714957) to blackcurrant purple (#422F45) in both water and 5% KOH, with a small apiculus, with an indistinct germ pore. Basidia 21–25 × 6–7 μm, clavate, 4-spored, thin-walled, nearly colorless in both water and 5% KOH, with sterigmata up to 2 µm long, surrounding by basidioles measured 13–20 × 5–7 μm. Lamella trama regular to subregular, composed of 4–9 µm wide, cylindrical to subcylindrical, thin-walled, nearly colorless in both water and 5% KOH, compact, moderately to frequently branching hyphae; gloeoplerous hyphae present, almost non-septate, tinged brick orange (#ECE2B4) to light brown (#B39966) in both water and 5% KOH. Cheilocystidia moderately abundant to abundant, 15–19 × 4–7 µm, narrowly ovoid to clavate, thin-walled, smooth, nearly colorless in both water and 5% KOH. Pleurocystidia absent. Pileus squamules subhymeniform, hymeniform to intricate trichoid at center, becoming entirely intricate trichoid towards margin, composed of slightly thick-walled and encrusted, globose, subglobose, broadly ellipsoid, ellipsoid to clavate cells measured 11–22 × 9–14 µm or subcylindrical to cylindrical, interwoven, moderately to frequently branching hyphae 2–7 µm wide, tinged pale beige brown (#E0CDA5) to pale meat brown (#E4C8BB) in both water and 5% KOH. Stipe squamules intricate trichoid, composed of slightly thick-walled and encrusted, subcylindrical to cylindrical, interwoven, moderately to frequently branching hyphae 3–6 µm wide, tinged pale meat brown (#E4C8BB) in both water and 5% KOH. Clamp connections absent in all tissues.

Habitat and distribution:— Solitary to gregarious, scattered on soil as individuals in southern subtropical monsoon forests. Currently, it is known from China (South China), Malaysia, and Thailand.

Collections examined:— China, Guangdong Province, Guangzhou City, Tianhe District, South China Agricultural University , Arboretum , on soil, 23°09’19”N, 113°21’41”E, elevation 40 m, September 6, 2023, Kun L. Yang & Jia Y. Lin, L 23404 ( HTBM1385 (ITS: PP736734; nrLSU: PP732964; rpb2: PP746792; tef-1α: PP746820 )) ; same location, April 19, 2024, Jia Y. Lin, L 24091 ( HTBM1965 ) ; China, Guangdong Province, Guangzhou City, Haizhu District, Shangchong Fruit Trees Park , on soil, 23°04’36”N, 113°18’21”E, elevation 2 m, April 3, 2024, Jia Y. Lin, L 24051 ( HTBM1925 (ITS: PP736665; nrLSU: PP732895; rpb2: PP746800; tef-1α: PP746830 )) & L24053 ( HKAS133466 , partly isolated as HTBM1927 (ITS: PP736666; nrLSU: PP732896; tef-1α: PP746831 )) ; same location, April 4, 2024, Jia Y. Lin, L 24066 ( HTBM1940 (ITS: PP736670; nrLSU: PP732900 )) .

Additional notes: In the protologue of Heinemannomyces splendidissimus, Watling (1999) described “darker, red-brown, ellipsoid, 15–62 × 9–22 µm or subglobose cells 7–9 × 9–10 µm, loosely arranged in chains in mediopellis, supporting a suprapellis of twisted, flexuous, slightly thick-walled hyphae 3–6 µm broad some quite narrow with thickened walls and connected to rounded shorter cells”. The “ellipsoid or subglobose cells in mediopellis” are the epithelioid, subhymeniform to hymeniform elements, and the “twisted, flexuous, slightly thick-walled hyphae” are the hyphae forming an irregular trichoderm arising from the epithelioid, subhymeniform to hymeniform elements. However, it’s notable that some epithelioid, subhymeniform to hymeniform elements are terminated without the trichoderm-forming hyphae, strongly resembling those of the other Hymenagaricus species.

Watling (1999) found clamp connections in his collections. However, no clamp connections were observed in our collections, consistent with Hosen et al. (2017) and Yang et al. (2019).

In the current phylogeny ( Fig. 1 ), the collections of this species were located in the crown clade of Hymenagaricus . Based on the morphological characteristics and phylogenetic evidence, we transferred this species to the genus Hymenagaricus and amended its genus description to encompass species with bluish to purplish spores.

Figures

FIGURE 1. Phylogeny of Agaricaceae s. l. inferred from the concatenated ITS-nrLSU-rpb2-tef-1α dataset. The genus Xanthagaricus is collapsed and independently displayed in Fig. 2. Nodes are annotated if supported by ≥50% MLB or ≥0.9 BPP. Branches shortened to fit the page are indicated by two diagonal lines with the number of times that they are shortened. Each phylogenetic genus is highlighted with a background color. Collections sequenced in this study are highlighted in purple. Holotype collections are indicated by HT.

FIGURE 3. Hymenagaricus splendidissimus (Photosby JiaY.Lin &Kun L.Yang;drawings by Kun L.Yang &JiaY.Lin,from HTBM1925, HTBM1385 & HKAS133466). a–h. Basidiomata from immature to mature (a–b. HTBM1925; c–d. HTBM1385; e–f. HKAS133466; g. HTBM1940; h. HTBM1965, yellow arrow indicates the flaky squamules microscopically dominated by hymeniform elements at pileus center). i. A hypha arising from hymeniform elements in pileus squamules under LM. j. Longitudinal section of pileus; yellow arrows trace the layer of flaky squamules microscopically dominated by hymeniform elements, limited at the pileus center and beneath the floccose to fibrous squamules microscopically dominated by hyphae forming an irregular trichoderm. k. Line drawing of the squamules at the pileus center.l–m. Basidiospores (l. SEM photo of HKAS133466; m. Line drawing). n. Hymenium and subhymenium. o. Cheilocystidia. p. Stipe squamules. Bars: a–b = 5 mm, c–d = 10 mm, e–h = 20 mm, i, k = 20 µm, l–m = 5 µm, n–o = 10 µm, p = 20 µm.