Xanthagaricus boluoshanensis Kun L. Yang, Jia Y. Lin, Zhen-Chao Liu & 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 : 127-129

Xanthagaricus boluoshanensis Kun L. Yang, Jia Y. Lin, Zhen-Chao Liu & Zhu L. Yang , sp. nov. ( Fig. 4 )

Registration identifier:— FN571938

Etymology:— Named after Boluoshan (Chinese, meaning pineapple hill), where all collections of this species examined in this study were found.

Diagnosis:— Differing from other Asian Xanthagaricus species by a combination of pileus 2.5–9 mm in diameter, with yellowish, orangish, reddish to brownish squamules, and ellipsoid to oblong, smooth basidiospores.

Type:— China, Guangdong Province, Guangzhou City, Huangpu District, Jiangdong Village , Boluoshan Hill , on soil, 23°11’31”N, 113°32’48”E, elevation 150 m, June 23, 2023, Zhen-Chao Liu, Kun L. Yang & Jia Y. Lin, S 23183 ( HKAS133457 , holotype! (ITS: PP736737; nrLSU: PP732967; tef-1α: PP746834 ); HTBM0426 , isotype!) .

Description:— Basidiomata tiny. Pileus 2.5–9 mm in diameter, hemispherical to convex, slightly umbonate; background ceramic white (#FEFEFA); squamules flaky to granular, thatch yellow (#F1ECC5), dull thatch yellow (#D3D3B7), bright teak brown (#AF9C6D), tea orange (#EFDFA0), earthy orange (#CF8A45) to dirty brass brown (#B47F5A), becoming lighter towards margin; margin with distinct but fugacious appendices concolorous with the squamules on the pileus or butter orange (#F2DF8F), dull dirty orange (#EBD087) to bright earthy orange (#E3B163) colored; context ceramic white (#FEFEFA) to merino white (#F9F5EC) when fresh, without a color change or becoming darker after damaged. Lamellae free, nearly crowded, ceramic white (#FEFEFA), pale beige brown (#E0CDA5), heathered brown (#B7AB8F) to dull silver gray (#A7A6A5), with an entire to slightly serrate edge; lamellulae abundant. Stipe 18–39 mm long, 1–1.5 mm thick, cylindrical to subcylindrical, sometimes tapering downwards, slightly curved; background medium gray (#E0DEDD), reef brown (#CCC2A6) to lacewood brown (#D5B7A1); squamules fibrous, usually more abundant below the annulus, ceramic white (#FEFEFA) to thatch yellow (#F1ECC5); context ceramic white (#FEFEFA) to merino white (#F9F5EC) when fresh, without a color change or becoming darker after damaged; base with moderately abundant tomenta. Annulus superior, easily broken and fugacious, concolorous with the squamules on the stipe. Odor fungal. Taste unknown.

Basidiospores [40/4/3] (4.5) 5–5.5 [5.16 ± 0.28, 5.00] × 3–3.5 [3.05 ± 0.15, 3.00] µm, Q = (1.43) 1.50–1.83 [1.70 ± 0.10, 1.67], ellipsoid to oblong, slightly thick-walled, smooth under both LM and SEM, tinged brick orange (#ECE2B4) to pumpkin orange (#CEB640) in both water and 5% KOH, with a small apiculus, without a germ pore. Basidia 11–16 × 3.5–6 μm, clavate to subcylindrical, 4-spored, thin-walled, nearly colorless in both water and 5% KOH, with sterigmata up to 2 µm long, surrounding by basidioles measured 11.5–14 × 4–5.5 μm. Lamella trama subregular, composed of 4–9 µm wide, subcylindrical, thin-walled, nearly colorless in both water and 5% KOH, compact, frequently branching hyphae. Cheilocystidia abundant, 9–17 × 5–8 µm, clavate to subcylindrical, thin-walled, smooth, nearly colorless in both water and 5% KOH. Pleurocystidia absent. Pileus squamules epithelioid, composed of globose to subglobose, slightly thick-walled and encrusted cells measured 8–23 × 7–18.5 µm, tinged pale beige brown (#E0CDA5) in both water and 5% KOH. Stipe squamules intricate trichoid, composed of 3–5.5 (7) µm wide, interwoven, flexuous, thin- to slightly thick-walled and encrusted, moderately to frequently branching hyphae, tinged cardamon yellow (#E0E091) in both water and 5% KOH. Clamp connections absent in all tissues.

Habitat and distribution:— Gregarious, usually strongly caespitose, scattered on the soil as clusters, in southern subtropical monsoon forests. Currently known from China (South China).

Additional collections examined:— China, Guangdong Province, Guangzhou City, Huangpu District, Jiangdong Village , Boluoshan Hill , on soil, 23°11’31”N, 113°32’48”E, elevation 150 m, June 23, 2023, Zhen-Chao Liu, Kun L. Yang & Jia Y. Lin, S 23185 ( HTBM0428 (ITS: PP736739; nrLSU: PP732969; tef-1α: PP746835 )) ; same location, April 16, 2024, Zhen-Chao Liu, Kun L. Yang & Jia Y. Lin, S 24009 ( HTBM1975 ) .

Figures

FIGURE 4. Xanthagaricus boluoshanensis (Photos by Zhen-Chao Liu & Kun L. Yang; drawings by Kun L. Yang & Jia Y. Lin, from HKAS133457 (holotype)). a–e. Basidiomata from immature to mature (a–c. HTBM1975; d–e. HKAS133457 (holotype)). f. Squamules at pileus center. g. Stipe squamules. h. Hymenium and subhymenium. i. Cheilocystidia. j–k. Basidiospores (j. SEM photo of HKAS133457; k. Line drawing). Bars: a–e = 10 mm, f–g = 20 µm, h–k = 5 µm.