Xanthagaricus phylononcaeruleus 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 : 140-142

Xanthagaricus phylononcaeruleus Kun L. Yang, Jia Y. Lin, Zhen-Chao Liu & Zhu L. Yang , sp. nov. ( Fig. 12 )

Registration identifier:— FN571943

Etymology:— Structured from “ phylo -non - caeruleus ”, as this species is phylogenetically not recognized as X. caeruleus , but is morphologically very similar to X. caeruleus .

Diagnosis:— Similar to X. caeruleus , but differing from it by a shorter stipe (up to 24 mm) and narrower cheilocystidia (up to 10 μm wide).

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, April 23, 2023, Kun L.Yang & Jia Y. Lin, K 23155 ( HKAS133456 , holotype! (ITS: PP736698; nrLSU: PP732928; rpb2: PP746785; tef-1α: PP746804 ); HTBM0670 , isotype!) .

Description:— Basidiomata small. Pileus 10–14 mm in diameter, hemispherical to plano-convex; background alabaster white (#F9F9F9) to overcast blue (#D6DBE7); squamules more or less flaky at center, becoming granular towards margin, dirty wisteria violet (#C5BCCC), steak purple (#877280), rosewood red (#78545C), blackcurrant purple (#422F45) to dull thatch red (#B29B9C), becoming lighter towards margin; margin with appendices concolorous with or lighter than the squamules on the pileus; context ceramic white (#FEFEFA) to merino white (#F9F5EC) when fresh, turning rust orange (#D79A65) or becoming darker after damaged. Lamellae free, subdistant to nearly crowded, alabaster white (#F9F9F9), dirty sky blue (#BED5DB) to sand green (#B2C4B5), with an entire to slightly serrate edge; lamellulae abundant. Stipe 16–24 mm long, 1.5–2 mm thick, cylindrical, slightly curved; background alabaster white (#F9F9F9) to lacewood brown (#D5B7A1); squamules fibrous to woolly, usually more abundant below the annulus, dirty wisteria violet (#C5BCCC) to desert orange (#E8D7B0); context ceramic white (#FEFEFA) to merino white (#F9F5EC) when fresh, turning rust orange (#D79A65) or becoming darker after damaged; base without tomenta. Annulus superior, easily broken and fugacious, concolorous with the squamules on the stipe. Odor fungal. Taste fungal.

Basidiospores [40/3/3] (5) 5.5–6 [5.81 ± 0.27, 6.00] × 3–3.5 [3.14 ± 0.22, 3.00] µm, Q = 1.57–2.00 [1.86 ± 0.15, 2.00], ellipsoid to oblong, slightly thick-walled, smooth under both LM and SEM, tinged ink green (#9DB1A7) to pale slate blue (#688D99) in both water and 5% KOH, with a small apiculus, with an indistinct germ pore. Basidia 8–15.5 × 5–7 μm, clavate to broadly clavate, 4-spored, thin-walled, nearly colorless in both water and 5% KOH, with sterigmata up to 2 µm long, surrounding by basidioles measured 7.5–14 × 3–7 μm. Lamella trama regular to subregular, composed of 3–11 µm wide, cylindrical to subcylindrical, thin-walled, nearly colorless in both water and 5% KOH, compact, moderately to frequently branching hyphae. Cheilocystidia very abundant, 18–26 × 7–10 µm, clavate, oblong to subcylindrical, thin-walled, smooth, nearly colorless in both water and 5% KOH. Pleurocystidia absent. Pileus squamules epithelioid, composed of globose, subglobose, ovoid to clavate, slightly thick-walled and encrusted cells measured 4.5–20 × 4.5–10 µm, tinged barley orange (#E4C8A4) in both water and 5% KOH. Stipe squamules intricate trichoid, composed of 3–10 µm wide, interwoven, flexuous, thin- to slightly thick-walled and encrusted, moderately to frequently branching hyphae, tinged pale brown (#E3DECC) in both water and 5% KOH. Clamp connections absent in all tissues.

Habitat and distribution:— Solitary to gregarious, seldom weakly caespitose, usually scattered on soil as individuals, in southern subtropical monsoon forests or 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, June 30, Jia Y. Lin, L 23127 ( HTBM0960 (ITS: PP736710; nrLSU: PP732940 )) ; same location, August 25, Jia Y. Lin, L 23318 ( HTBM1299 (ITS: PP736715; nrLSU: PP732945; rpb2: PP746802; tef-1α: PP746838 )) ; same location, August 27, Jia Y. Lin, L 23323 ( HTBM1304 (ITS: PP736717; nrLSU: PP732947; rpb2: PP746786; tef-1α: PP746805 )) ; same location, August 30, Jia Y. Lin , L23339 ( HTBM1320 (ITS: PP736720; nrLSU: PP732950 )), L23340 ( HTBM1321 (ITS: PP736721; nrLSU: PP732951 )) & L23346 ( HTBM1327 (ITS: PP736724; nrLSU: PP732954 )) ; same location, August 31, Jia Y. Lin, L 23355 ( HTBM1336 (ITS: PP736725; nrLSU: PP732955 )) & L23356 ( HTBM1337 (ITS: PP736726; nrLSU: PP732956 )) ; same location, September 4, Jia Y. Lin, L 23378 ( HTBM1359 (ITS: PP736731; nrLSU: PP732961 )) ; same location, September 18, Jia Y. Lin, L 23444 ( HTBM1425 (ITS: PP736735; nrLSU: PP732965 )) ; China, Guangdong Province, Guangzhou City, Huangpu District, Jiangdong Village , Boluoshan Hill , on soil, 23°11’31”N, 113°32’48”E, elevation 150 m, August 27, 2023, Zhen-Chao Liu, Kun L. Yang & Jia Y. Lin, S 23554 ( HTBM1665 (ITS: PP736745; nrLSU: PP732975 )) ; same location, August 28, 2023, Zhen-Chao Liu, Kun L. Yang & Jia Y. Lin, S23569 ( HTBM1680 (ITS: PP736750; nrLSU: PP732980 )) ; same location, August 31, 2023, Zhen-Chao Liu, Kun L. Yang & Jia Y. Lin, S23572 ( HTBM1683 (ITS: PP736751; nrLSU: PP732981 )) & S23573 ( HTBM1684 (ITS: PP736752; nrLSU: PP732982 )) ; same location, September 6, 2023, Zhen-Chao Liu, Kun L. Yang & Jia Y. Lin, S23588 ( HTBM1699 (ITS: PP736753; nrLSU: PP732983 )), S23589 ( HTBM1700 (ITS: PP736754; nrLSU: PP732984 )), S23590 ( HTBM1701 (ITS: PP736755; nrLSU: PP732985 )) & S23591 ( HTBM1702 (ITS: PP736756; nrLSU: PP732986 )) .

Additional notes: In the current phylogeny ( Fig. 2 ), our collections mainly gathered from two different regions in Guangzhou, formed a stable clade with little internal variation and significant support (MLB=100%, BPP=1), presenting a distinct genetic distance from the clade formed by the holotype and paratype of X. caeruleus . Three species delimitation programs consistently supported these two groups to be two separate species, suggesting our collections represent a cryptic species of the X. caeruleus complex; thus, it’s named here as X. phylononcaeruleus . Stipe length and cheilocystidia width could be used to distinguish the two species.

It’s also notable that the stipe of X. phylononcaeruleus distinctly turns rust orange after damaged ( Fig. 12m ). This reaction is not mentioned in the description in the protologue of X. caeruleus ( Hosen et al. 2018) , but as shown in the photo in the protologue (the Fig. 2A in Hosen et al. 2018), X. caeruleus may also have this character. When mature, the stipe of X. phylononcaeruleus also presents an orangish to brownish tinge; it could be the result of a slow oxidation, essentially the same mechanism of the reaction after damage.

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 12. Xanthagaricus phylononcaeruleus (Photos by Zhen-Chao Liu, Jia Y. Lin & Kun L. Yang; drawings by Kun L. Yang & Jia Y. Lin, from HKAS133456 (holotype)). a–m. Basidiomata (a. HTBM1299; b. HKAS133456 (holotype); c–d. HTBM1304; e. HTBM1320; f. HTBM1327; g. HTBM1337; h. HTBM1702; i–j. HTBM1665; k–m. HTBM1680, note the stipes in m distinctly becoming rust orange after touched; n–o. HTBM1684). p–q. Basidiospores (p. Line drawing; q. SEM photo of HKAS133456 (holotype)). r. Hymenium and subhymenium. s. Cheilocystidia. t. Squamules at pileus center. u. Stipe squamules. Bars: a–b, e–k, m–o = 10 mm, c–d = 5 mm, l = 20 mm, p–r = 5 µm, s–t = 10 µm, u = 20 µm.