Xanthagaricus guangzhouensis 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 : 133

Xanthagaricus guangzhouensis Kun L. Yang, Jia Y. Lin & Zhu L. Yang , sp. nov. ( Fig. 7 )

Registration identifier:— FN571940

Etymology:— Named after Guangzhou, the city where the holotype of this species was collected.

Diagnosis:— Similar to X. chamaeleontinus and X. ianthinus , but differing from them by brownish squamules on stipe and bluish lamellae.

Type:— China, Guangdong Province, Guangzhou City, Nansha District, Huangshanlu Forest Park , a green belt along Dengshan Rd. , on soil, 22°46’22”N, 113°34’21”E, elevation 90 m, April 15, 2023, Kun L. Yang & Jia Y. Lin, K 23116 ( HKAS133455 , holotype! (ITS: PP736697; nrLSU: PP732927; tef-1α: PP746818 ); HTBM0631 , isotype!) .

Description:— Basidiomata tiny. Pileus 5–8 mm in diameter, hemispherical to convex; background conch white (#EFEFF7) to periwinkle blue (#CDCFE5); squamules more or less flaky at center, becoming granular towards margin, wisteria violet (#C5BBDC) to rosewood red (#78545C), becoming lighter towards margin; margin with appendices conch white (#EFEFF7); context ceramic white (#FEFEFA) to merino white (#F9F5EC) when fresh, without a color change or becoming darker after damaged. Lamellae free, subdistant to nearly crowded, pale periwinkle blue (#C9D4E6) to dull pigeon blue (#A9B5C3), with a slightly serrate edge; lamellulae abundant. Stipe 7–10 mm long, 1 mm thick, cylindrical, slightly curved; background ceramic white (#FEFEFA) to pale bone brown (#E7D5C7); squamules furfurous, usually more abundant below the annulus, merino white (#F9F5EC), lacewood brown (#D5B7A1) to mire brown (#B89F89); context ceramic white (#FEFEFA) to merino white (#F9F5EC) when fresh, turning sandal brown (#BA8B70) or becoming darker after damaged; base without tomenta. Annulus superior, easily broken and fugacious, concolorous with the squamules on the stipe. Odor unknown. Taste unknown.

Basidiospores [40/2/2] 4–5 [4.26 ± 0.35, 4.00] × 2.5–3 (3.5) [2.94 ± 0.23, 3.00] µm, Q = (1.29) 1.33–1.67 [1.46 ± 0.13, 1.33], broadly ellipsoid to ellipsoid, slightly thick-walled, smooth under both LM and SEM, tinged withered green (#D5DCB7) to muck green (#92A890) in both water and 5% KOH, with a small apiculus, without a germ pore. Basidia 11–13.5 × 5–6 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 10–15 × 3.5–5.5 μm. Lamella trama regular to subregular, composed of 4–11 µm wide, cylindrical to subcylindrical, thin-walled, nearly colorless in water and 5% KOH, compact, moderately to frequently branching hyphae. Cheilocystidia very abundant, 12.5–26 × 4–8 µm, clavate, ovoid, subcylindrical to slightly flexuose, thin-walled, smooth, nearly colorless in both water, and 5% KOH. Pleurocystidia absent. Pileus squamules epithelioid, composed of globose, subglobose to broadly ellipsoid, slightly thick-walled and encrusted cells measured 8–16 × 7.5–13 µm, tinged tea orange (#EFDFA0) in both water and 5% KOH. Stipe squamules structured as the same as the pileus squamules but brighter-colored, tinged butter orange (#F2DF8F) in both water and 5% KOH. Clamp connections absent in all tissues.

Habitat and distribution:— Solitary to gregarious, seldom weakly caespitose, scattered on the soil as individuals, in urban green belts. Currently known from China (South China).

Additional collection examined:— China, Guangdong Province, Guangzhou City, Nansha District, Huangshanlu Forest Park , a green belt along Dengshan Rd. , on soil, 22°46’22”N, 113°34’21”E, elevation 90 m, April 15, 2023, Kun L. Yang & Jia Y. Lin, K 23117 ( HTBM0632 (ITS: PP736657; nrLSU: PP732888; tef-1α: PP746819 )) .

Additional notes: This species is rare. After we got the two collections on April 15, 2023, we haven’t seen it again, even at the locality where it was found originally.

Figures

FIGURE 7. Xanthagaricus guangzhouensis (Photos by Kun L. Yang; drawings by Kun L. Yang & Jia Y. Lin, from HKAS133455 (holotype)). a–c. Basidiomata from immature to mature (a. HTBM0632; b–c. HKAS133455 (holotype)). d. Squamules at pileus center. e. Stipe squamules. f. Hymenium and subhymenium. g. Cheilocystidia. h–i. Basidiospores (h. SEM photo of HKAS133455 (holotype); i. Line drawing). Bars: a–c = 5 mm, d–e = 10 µm, f–g, i = 5 µm, h = 2 µm.