Xanthagaricus scauinus 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 : 146-147

Xanthagaricus scauinus Kun L. Yang, Jia Y. Lin & Zhu L. Yang , sp. nov. ( Fig. 15 )

Registration identifier:— FN571945

Etymology:— Named after South China Agricultural University, where all collections of this species examined in this study were found.

Diagnosis:— Differing from other Asian Xanthagaricus species by a combination of not strongly caespitose basidiomata, pileus 4.5–7 mm in diameter, with yellowish to orangish but not brownish, reddish, or greenish squamules, and basidiospores mostly ellipsoid to oblong, rarely ovoid, with sparsely verrucose ornamentation.

Type:— China, Guangdong Province, Guangzhou City, Tianhe District, South China Agricultural University , a green belt in front of the College of Forestry and Landscape Architecture , on soil, 23°09’35”N, 113°21’39”E, elevation 30 m, September 4, 2023, Jia Y. Lin, L 23379 ( HKAS133463 , holotype! (ITS: PP736732; nrLSU: PP732962 ); HTBM1360 , isotype!) .

Description:— Basidiomata tiny. Pileus 4.5–7 mm in diameter, hemispherical to plano-convex; background pale milky orange (#FFEDA2); squamules mostly granular, occasionally flaky, pale milky orange (#FFEDA2), goldenrod orange (#F9D873) to bright caramel orange (#EB9300), becoming lighter towards margin; margin with appendices concolorous with the squamules on the pileus; context ceramic white (#FEFEFA) to merino white (#F9F5EC) when fresh, becoming darker after damaged. Lamellae free, subdistant to nearly crowded, pale milky orange (#FFEDA2) to caramel orange (#DB8E37), with an entire to slightly serrate edge; lamellulae abundant. Stipe cylindrical to subcylindrical, sometimes tapering downwards, slightly curved, 8–12 mm long, 0.5–1 mm thick; background ceramic white (#FEFEFA), medium gray (#E0DEDD), pale milky orange (#FFEDA2) to dull golden orange (#D8B77B); squamules woolly to furfurous, usually more abundant below the annulus, pale milky orange (#FFEDA2) to bright caramel orange (#EB9300); context ceramic white (#FEFEFA) to merino white (#F9F5EC) when fresh, 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 mostly ellipsoid to oblong, rarely ovoid, slightly thick-walled, smooth under LM, sparsely verrucose under SEM, tinged moon yellow (#FAF9AA) to lion orange (#EFD871) in both water and 5% KOH, [40/4/4] 4.5–5.5 [4.96 ± 0.28, 5.00] × 2.5–3.5 [2.99 ± 0.24, 3.00] µm, Q = 1.43–2.00 [1.67 ± 0.15, 1.67], with a small apiculus, without a germ pore. Basidia clavate, 4-spored, thin-walled, nearly colorless in both water and 5% KOH, 11–13 × 5–6 μm, with sterigmata up to 2 µm long, surrounding by basidioles measured 9–12 × 3–5 μm. Lamella trama regular to subregular, composed of 4–11 (14) µm wide, cylindrical, subcylindrical to broadly ellipsoid, thin-walled, nearly colorless in both water and 5% KOH, compact, moderately to frequently branching hyphae. Cheilocystidia very abundant, subcylindrical to flexuose, thin-walled, smooth, nearly colorless in both water and 5% KOH, 13–19.5 × 3–5 µm. Pleurocystidia absent. Pileus squamules epithelioid, composed of globose, subglobose to broadly ellipsoid, slightly thick-walled and encrusted cells measured 9–20 × 8–25 µm, tinged mana yellow (#F7F57E) to butter orange (#F2DF8F) in both water and 5% KOH. Stipe squamules structured as the same as the pileus squamules but darker-colored, tinged cardamon yellow (#E0E091) in both water and 5% KOH. Clamp connections absent in all tissues.

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

Additional collections examined:— China, Guangdong Province, Guangzhou City, Tianhe District, South China Agricultural University , a green belt in front of the College of Forestry and Landscape Architecture , on soil, 23°09’35”N, 113°21’39”E, elevation 30 m, May 13, 2023, Kun L. Yang & Jia Y. Lin, K 23199 ( HTBM0714 (ITS: PP736700; nrLSU: PP732930; rpb2: PP746787; tef-1α: PP746808 )) ; same location, June 13, 2023, Jia Y. Lin, L 2383 ( HTBM0916 (ITS: PP736736; nrLSU: PP732966; tef-1α: PP746807 )) ; same location, June 27, 2023, Jia Y. Lin, L 23102 ( HTBM0935 (ITS: PP736703; nrLSU: PP732933; tef-1α: PP746806 )), L23105 ( HTBM0938 (ITS: PP736705; nrLSU: PP732935 )) & L23111 ( HTBM0944 (ITS: PP736709; nrLSU: PP732939 )) ; same location, June 30, 2023, Jia Y. Lin, L 23130 ( HTBM0963 (ITS: PP736711; nrLSU: PP732941 )) ; same location, August 25, 2023, Jia Y. Lin, L 23322 ( HTBM1303 (ITS: PP736716; nrLSU: PP732946 )) ; same location, August 30, 2023, Jia Y. Lin, L 23341 ( HTBM1322 (ITS: PP736722; nrLSU: PP732952 )) ; China, Guangdong Province, Guangzhou City, Tianhe District, South China Agricultural University , a lawn along Sweetheart Rd. , on soil, 23°09’21”N, 113°21’19”E, elevation 35 m, April 10, 2024, Kun L. Yang & Jia Y. Lin, L 24081 ( HTBM1955 (ITS: PP736689; nrLSU: PP732919 )) .

Figures

FIGURE 15. Xanthagaricus scauinus (Photos by Jia Y. Lin & Kun L. Yang; drawings by Kun L. Yang & Jia Y. Lin, from HKAS133463 (holotype)&HTBM0714).a–g.Basidiomata (a.HTBM0714;b–c.HTBM0963;d.HTBM0944;e.HTBM0935;f.HKAS133463 (holotype); g. HTBM1955). h. Cheilocystidia. i. Squamules at pileus center. j–k. Basidiospores (j. Line drawing; k. SEM photo of HKAS133463 (holotype)). l. Hymenium and subhymenium. m. Stipe squamules. Bars: a–f = 5 mm, g = 10 mm, h, j, l = 5 µm, i, m = 20 µm, k = 2 µm.