Xanthagaricus ianthinus Y. Li & F.J. Wang, Phytotaxa

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 : 136-138

Xanthagaricus ianthinus Y. Li & F.J. Wang, Phytotaxa 371(4): 242 (2018) ( Fig. 9 )

Description:— Basidiomata tiny. Pileus 3.5–7 mm in diameter, hemispherical, plano-convex to applanate, occasionally slightly umbonate; background zircon white (#F3F5FD) to conch white (#EFEFF7), becoming lighter towards margin; squamules mostly granular, occasionally woolly, wisteria violet (#C5BBDC), lisianthus violet (#846994) to blackcurrant purple (#422F45), sometimes turning rosewood red (#78545C) when mature, becoming lighter towards margin; margin with appendices zircon white (#F3F5FD) to merino white (#F9F5EC); 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, ceramic white (#FEFEFA) to dull silk brown (#C3B3A6), with a slightly serrate edge; lamellulae abundant. Stipe 12–24 mm long, 1 mm thick, subcylindrical, tapering downwards, slightly curved; background ceramic white (#FEFEFA), medium gray (#E0DEDD) to reef brown (#CCC2A6); squamules woolly, usually more abundant below the annulus, alabaster white (#F9F9F9) to ceramic white (#FEFEFA); context ceramic white (#FEFEFA) to merino white (#F9F5EC) when fresh, turning rust orange (#D79A65) or becoming darker after damaged; base without or with few tomenta. Annulus superior, easily broken and fugacious, concolorous with the squamules on the stipe. Odor fungal. Taste unknown.

Basidiospores [40/2/2] 4–5 [4.48 ± 0.22, 4.50] × 3–3.5 [3.19 ± 0.24, 3.00] µm, Q = (1.14) 1.29–1.50 [1.41 ± 0.11, 1.50], lacrymoid, phaseoliform, ovoid to ellipsoid in side view, ovoid to ellipsoid in frontal view, slightly thick-walled, smooth under both LM and SEM, tinged milky yellow (#FFF07A) to golden orange (#E4CB4E) in both water and 5% KOH, with a small apiculus, without a germ pore. Basidia 10.5–14 × 5–6.5 μm, clavate, mostly 4-spored, occasionally 2-spored, thin-walled, nearly colorless in both water and 5% KOH, with sterigmata up to 2 µm long, surrounded by basidioles measured 5–11 × 4–5.5 μm. Lamella trama regular to subregular, composed of 3.5–11 µm wide, cylindrical to subcylindrical, thin-walled, nearly colorless in water and 5% KOH, compact, moderately to frequently branching hyphae. Cheilocystidia very abundant, 13–19 × 6.5–10.5 µm, clavate to broadly clavate, thin-walled, smooth, and nearly colorless in water and 5% KOH. Pleurocystidia absent. Pileus squamules epithelioid, composed of globose, subglobose to broadly ellipsoid, slightly thick-walled, and encrusted cells measured 8.5–19 × 8–16 µm, tinged cotton brown (#D2CAAD) in both water and 5% KOH. Stipe squamules intricate trichoid, composed of 2.5–6 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:— Solitary, scattered on soil as individuals, in southern subtropical monsoon forests. Currently known from China (Central and South China).

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 23185B ( HTBM1974 (ITS: PP736696; nrLSU: PP732926; tef-1α: PP746837 )) ; same location, August 27, 2023, Zhen-Chao Liu, Kun L. Yang & Jia Y. Lin, S23540 ( HTBM1651 (ITS: PP736743; nrLSU: PP732973 )) ; same location, August 28, 2023, Zhen-Chao Liu, Kun L. Yang & Jia Y. Lin, S23566 ( HKAS133452 , partly isolated as HTBM1677 (ITS: PP736746; nrLSU: PP732976 )) & S23566B (completely used up (ITS: PP736747; nrLSU: PP732977 )) ; same location, April 12, 2024, Zhen-Chao Liu, Kun L. Yang & Jia Y. Lin, S24005 ( HTBM1970 (ITS: PP736692; nrLSU: PP732922 )), S24006 ( HTBM1971 (ITS: PP736693; nrLSU: PP732923 )) & S24007 ( HTBM1972 (ITS: PP736694; nrLSU: PP732924 )) .

Additional notes: The morphology of our collections fits the protologue of X. ianthinus well. However, in the current phylogeny ( Fig. 2 ), our six collections formed a clade with relatively distinct genetic distance to the clade formed by the holotype and paratype of X. ianthinus ; each clade with significant support. The ABGD program suggested the clade of our collections to 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 differences between our description and the protologue were not found, we treated our collections as X. ianthinus for the moment.

This species is very similar to X. chamaeleontinus . For a comparison between them, see the Diagnosis of X. chamaeleontinus above. Also similar to the case in X. chamaeleontinus , the basidiospore shape of this species was variable under LM and did not change even after being soaked in 5% KOH for an hour. The observation under SEM showed that it’s caused by the drying of the collections; thus, the basidiospore measurements not totally from fresh collections are inappropriate for characterizing this species, including those measured above.

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 9. Xanthagaricus ianthinus (Photos by Zhen-Chao Liu & Kun L.Yang; drawings by Kun L.Yang & JiaY. Lin, from HTBM1651). a–g. Basidiomata (a. HTBM1651; b. HTBM1970; c–d. HTBM1970; e. HTBM1971; f–g. HTBM1972). h. Cheilocystidia. i. Squamules at pileus center. j. Hymenium and subhymenium. k–l. Basidiospores (k. Line drawing; l. SEM photo of HTBM1651). m. Stipe squamules. Bars: a–b, f–g = 5 mm, c–e = 2 mm, h–i, m = 10 µm, j–k = 5 µm, l = 2 µm.