Xanthagaricus necopinatus Iqbal Hosen, T.H. Li & G.M. Gates, MycoKeys

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 : 139-140

Xanthagaricus necopinatus Iqbal Hosen, T.H. Li & G.M. Gates, MycoKeys 28: 9 (2017) ( Fig. 11 )

Description:— Basidiomata tiny to small. Pileus 7–16 mm in diameter, hemispherical to plano-convex, sometimes slightly umbonate when mature; background ceramic white (#FEFEFA), beach yellow (#F9F3C9) to desert orange (#E8D7B0), becoming lighter towards margin; squamules granular to furfurous, loquat orange (#F3D390), sandy orange (#E6CF73) to light brown (#B39966), becoming lighter towards margin; margin with appendices concolorous with the squamules on the pileus; context ceramic white (#FEFEFA) to merino white (#F9F5EC) when fresh, turning rust orange (#D79A65) to sandal brown (#BA8B70) after damaged. Lamellae free, nearly crowded, ceramic white (#FEFEFA) to pale bone brown (#E7D5C7), with a slightly serrate edge; lamellulae abundant. Stipe 19–30 mm long, 1–2 mm thick, cylindrical to subcylindrical, sometimes tapering downwards, slightly curved; background ceramic white (#FEFEFA), beach yellow (#F9F3C9) to desert orange (#E8D7B0); squamules furfurous, usually more abundant below the annulus, ceramic white (#FEFEFA) to beach yellow (#F9F3C9); context ceramic white (#FEFEFA) to merino white (#F9F5EC) when fresh, turning rust orange (#D79A65) to sandal brown (#BA8B70) after damaged; base without tomenta. Annulus superior, easily broken and fugacious, concolorous with the squamules on the stipe. Odor strongly fungal. Taste unknown.

Basidiospores [40/2/2] 4–4.5 (5) [4.45 ± 0.19, 4.50] × (2.5) 3 (3.5) [3.01 ± 0.14, 3.00] µm, Q = (1.29) 1.33–1.50 (1.67) [1.48 ± 0.07, 1.50], mostly ellipsoid, rarely broadly ellipsoid or oblong, slightly thick-walled, smooth under LM, densely verrucose under SEM, tinged cardamon yellow (#E0E091) to dusk orange (# CEAD 64) in both water and 5% KOH, with a small apiculus, without a germ pore. Basidia 12–15 × 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 8–11 × 4–5.5 μm. Lamella trama subregular, composed of 3–7 µm wide, cylindrical to subcylindrical, thin-walled, nearly colorless in both water and 5% KOH, compact, moderately to frequently branching hyphae. Cheilocystidia abundant, 9–15.5 × 5–7 µm, clavate, thin-walled, smooth, nearly colorless in both water and 5% KOH. Pleurocystidia absent. Pileus squamules epithelioid to subhymeniform, composed of globose, subglobose, ellipsoid to clavate, slightly thick-walled and encrusted cells measured 5–32 × 5–18 µm, tinged cardamon yellow (#E0E091) 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:— Gregarious, strongly caespitose, scattered on soil as clusters, in southern subtropical monsoon forests. Currently known from Bangladesh, China (South China) and Thailand.

Collections examined:— 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 7, 2024, Jia Y. Lin, L 24071 ( HKAS133468 , partly isolated as HTBM1945 (ITS: PP736685; nrLSU: PP732915 )), L24072 ( HTBM1946 (ITS: PP736686; nrLSU: PP732916 )) & L24073 ( HTBM1947 (ITS: PP736687; nrLSU: PP732917 )) .

Additional notes: The morphology of our collections almost fits the protologue of X. necopinatus , originally reported from Bangladesh, but has significantly shorter cheilocystidia (9–15.5 µm long) differing from the longer ones (15–20 µm long) described in the protologue ( Hosen et al. 2017). In the current phylogeny ( Fig. 2 ), our three collections plus a Thai collection consistently presented a relatively distinct genetic distance from the holotype of X. necopinatus , nested into a separate subclade significantly supported by MLB (MLB=85%). The ABGD program suggested this subclade represent a separate cryptic species, but the ASAP and PTP programs did not support this delimitation. Considering that these programs did not result in a consistent delimitation and that significant and stable differences between our description plus the description of the Thai collection ( Sysouphanthong et al. 2021, the cheilocystidia measured 17–25 µm long) and the protologue were not found, we treated our collections as X. necopinatus for the moment.

This is the first report of this species in China.

Figures

FIGURE 2. Phylogeny of Xanthagaricus, a part of the phylogeny of Agaricaceae s. l. inferred from the concatenated ITS-nrLSU-rpb2- tef-1α dataset in Fig. 1 (see also Supplement 3). 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. Collections sequenced in this study are highlighted in purple. Holotype collections are indicated by HT. The results of species delimitation generated from the ABGD, ASAP, and PTP programs, the accepted species delimitation, the type of basidiospore ornamentation, and the color of pileus squamules are shown on the right of the phylogenetic tree. New species proposed in this study are each annotated with a dot.

FIGURE 11. Xanthagaricus necopinatus (Photos by Jia Y.Lin & Kun L.Yang; drawings by Kun L.Yang & JiaY.Lin, from HKAS133468). a. Habitat of HKAS133468. b–g. Basidiomata (b–e. HKAS133468; f. HTBM1946; g. HTBM1947). h. Hymenium and subhymenium. i–j Basidiospores (i. Line drawing; j. SEM photo of HKAS133468).k. Cheilocystidia. l. Squamules at pileus center. m. Stipe squamules. Bars: b–c = 10 mm, d–e = 5 mm, f–g = 20 mm, h–i, k = 5 µm, j= 2 µm, l–m = 20 µm.