Xanthagaricus chamaeleontinus 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 : 129-133

Xanthagaricus chamaeleontinus Kun L. Yang, Jia Y. Lin, Zhen-Chao Liu & Zhu L. Yang , sp. nov. ( Fig. 5 )

Registration identifier:— FN571939

Etymology:— Named after chameleons, referring to the dramatic color changes of the pileus squamules of this species.

Diagnosis:— Similar to X. ianthinus , but differing from it by a shorter stipe (up to 14 mm), narrower cheilocystidia (up to 6.5 μm wide), and a pileus sometimes entirely turning brownish.

Type:— China, Guangdong Province, Guangzhou City, Huangpu District, Jiangdong Village , Boluoshan Hill , on soil, 23°11’31”N, 113°32’48”E, elevation 150 m, April 12, 2024, Zhen-Chao Liu, Kun L. Yang & Jia Y. Lin, S 24002 ( HKAS133454 , holotype! (ITS: PP736691; nrLSU: PP732921 ); HTBM1967 , isotype!) .

Description:— Basidiomata tiny. Pileus 4–7 mm in diameter, hemispherical, plano-convex to applanate, occasionally slightly umbonate; background conch white (#EFEFF7), becoming lighter towards margin; squamules mostly granular, occasionally flaky or woolly, wisteria violet (#C5BBDC), lisianthus violet (#846994) to blackcurrant purple (#422F45), sometimes entirely turning beaver brown (#9D7B69) 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 5–14 mm long, 0.5 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, 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 [40/3/3] (3.5) 4–5 [4.53 ± 0.27, 4.50] × (2.5) 3 (3.5) [3.01 ± 0.14, 3.00] µm, Q = (1.17) 1.33– 1.67 (1.80) [1.50 ± 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 golden orange (#E4CB4E) to pumpkin orange (#CEB640) in both water and 5% KOH, with a small apiculus, without a germ pore. Basidia 11.5–16.5 × 5.5–7 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, surrounding by basidioles measured 5–8 × 4–5.5 μm. Lamella trama regular to subregular, composed of 3–9 µm wide, cylindrical to subcylindrical, thin-walled, nearly colorless in water and 5% KOH, compact, moderately to frequently branching hyphae. Cheilocystidia moderately abundant, 11.5–17 × 4–6.5 µm, clavate to subcylindrical, 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 6.5–14 × 6.5–11.5 µm, tinged desert orange (#E8D7B0) in both water and 5% KOH. Stipe squamules intricate trichoid, composed of 2.5–9.5 µm wide, interwoven, flexuous, thin- to slightly thick-walled and encrusted, moderately to frequently branching hyphae, 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, 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, Nansha District, Huangshanlu Forest Park, a green belt along Dengshan Rd. , on soil, 22°46’22”N, 113°34’21”E, elevation 90 m, June 28, 2023, Kun L. Yang & Jia Y. Lin, K 23309 ( HTBM0824 (ITS: PP736701; nrLSU: PP732931; rpb2: PP746784; tef-1α: PP746803 )) ; China, Guangdong Province, Guangzhou City, Huangpu District, Jiangdong Village , Boluoshan Hill ,on soil, 23°11’31”N, 113°32’48”E, elevation 150 m, July 30, 2023, Zhen-Chao Liu, Kun L. Yang & Jia Y. Lin, L 23236 ( HKAS133451 , partly isolated as HTBM1188 (ITS: PP736712; nrLSU: PP732942 )) ; same location, August 16, 2023, Zhen-Chao Liu, Kun L. Yang & Jia Y. Lin, S23426 ( HTBM1537 (ITS: PP736647; nrLSU: PP732878 )) ; same location, August 21, 2023, Zhen-Chao Liu, Kun L. Yang & Jia Y. Lin, S23474 ( HTBM1585 (ITS: PP736740; nrLSU: PP732970 )) ; same location, August 23, 2023, Zhen-Chao Liu, Kun L. Yang & Jia Y. Lin, L23297 ( HTBM1278 (ITS: PP736713; nrLSU: PP732943 )) ; same location, August 25, 2023, Zhen-Chao Liu, Kun L. Yang & Jia Y. Lin, S23511 ( HTBM1622 (ITS: PP736741; nrLSU: PP732971 )) & S23519 ( HTBM1630 (ITS: PP736742; nrLSU: PP732972 )) ; same location, August 28, 2023, Zhen-Chao Liu, Kun L. Yang & Jia Y. Lin, S23567 ( HTBM1678 (ITS: PP736748; nrLSU: PP732978 )) ; same location, April 12, 2024, Zhen-Chao Liu, Kun L. Yang & Jia Y. Lin, S24001 ( HTBM1966 (ITS: PP736690; nrLSU: PP732920 )) & S24008 ( HTBM1973 (ITS: PP736695; nrLSU: PP732925 )) ; 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 4, 2024, Jia Y. Lin, L 24061 ( HTBM1935 (ITS: PP736678; nrLSU: PP732908 )), L24062 ( HTBM1936 (ITS: PP736679; nrLSU: PP732909 )) & L24063 ( HKAS133453 , partly isolated as HTBM1937 (ITS: PP736680; nrLSU: PP732910 )) .

Additional notes: 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. This problem also occurred in its sister species, X. ianthinus (see the description of X. ianthinus below).

Xanthagaricus erinaceus (Heinem. & Little Flower) Little Flower, Hosag. & T.K. Abraham , New Botanist 20(1–4): 96 (1997) ( Fig. 6 )

≡ Hymenagaricus erinaceus Heinem. & Little Flower , Bulletin du Jardin Botanique National de Belgique / Bulletin van de Nationale

Plantentuin van België 54(1–2): 178 (1984)

Description:— Basidiomata small. Pileus 15–31 mm in diameter, hemispherical to plano-convex; background ceramic white (#FEFEFA), pig white (#FDF7F2), chicken orange (#F8DCC9) to tumbleweed orange (#E8B28F); squamules more or less flaky at center, becoming granular, woolly to fibrous towards margin, tumbleweed orange (#E8B28F), barley brown (#E6D1B5), dirty brass brown (#B47F5A) to tangerine-peel orange (#CD6425), 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) after damaged. Lamellae free, crowded, linen brown (#E6DECB) to caramel orange (#DB8E37), with a slightly serrate edge; lamellulae abundant. Stipe 16–48 mm long, 1–2 mm thick, cylindrical, slightly curved; background ceramic white (#FEFEFA) to linen brown (#E6DECB); squamules fibrous, usually more abundant below the annulus, barley brown (#E6D1B5) to dirty brass brown (#B47F5A); context ceramic white (#FEFEFA) to merino white (#F9F5EC) when fresh, turning rust orange (#D79A65) 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] 4.5–5.5 [5.15 ± 0.30, 5.00] × 2.5–3.5 [3.05 ± 0.24, 3.00] µm, Q = (1.29) 1.43–2.00 [1.70 ± 0.16, 1.67], ellipsoid to oblong, slightly thick-walled, smooth under LM, sparsely verrucose under SEM, tinged milky yellow (#FFF07A) to golden orange (#E4CB4E) in both water and 5% KOH, with a small apiculus, without a germ pore. Basidia 12–15.5 × 5.5–7 μm, subcylindrical to clavate, mostly 4-spored, occasionally 2-spored, thin-walled, nearly colorless in both water and 5% KOH, with sterigmata up to 2 µm long, surrounding by basidioles measured 8–15 × 3.5–6 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, 7–26 × 2.5–7.5 µm, utriform to flexuous, thin-walled, smooth, and nearly colorless in water and 5% KOH. Pleurocystidia absent. Pileus squamules epithelioid, subhymeniform to hymeniform, composed of slightly thick-walled and encrusted, clavate to subcylindrical terminal cells measured 13–23.5 × 4.5–9 µm, on globose, subglobose to broadly ellipsoid cells measured 7–14.5 × 6–9 µm, tinged butter orange (#F2DF8F) in both water and 5% KOH. Stipe squamules intricate trichoid, composed of 2.5–4 µm wide, cylindrical to subcylindrical, thin- to slightly thick-walled and encrusted hyphae, tinged beach yellow (#F9F3C9) in both water and 5% KOH. Clamp connections absent in all tissues.

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

Collections examined:— China, Guangdong Province, Guangzhou City, Tianhe District, South China Agricultural University , a green belt in front of the College of Forestry and LandscapeArchitecture ,on soil, 23°09’35”N, 113°21’39”E, elevation 30 m, June 27, 2023, Jia Y. Lin, L 23103 ( HTBM0936 (ITS: PP736704; nrLSU: PP732934; rpb2: PP746788; tef-1α: PP746812 )), L23104 ( HTBM0937 (ITS: PP736641; nrLSU: PP732872 )), L23107 ( HTBM0940 (ITS:PP736706; nrLSU: PP732936; rpb2: PP746789; tef-1α: PP746813 )) & L23108 ( HTBM0941 (ITS: PP736707; nrLSU: PP732937; rpb2: PP746790; tef-1α: PP746814 )) ; same location, August 29, 2023, Jia Y. Lin, L 23331 ( HTBM1312 (ITS: PP736718; nrLSU: PP732948 )), L23332 ( HTBM1313 (ITS: PP736719; nrLSU: PP732949 )) & L23335 ( HTBM1316 ) ; same location, August 30, 2023, Jia Y. Lin, L 23342 ( HKAS133459 , partly isolated as HTBM1323 (ITS: PP736723; nrLSU: PP732953 )) ; same location, August 31, 2023, Jia Y. Lin, L 23357 ( HTBM1338 (ITS: PP736727; nrLSU: PP732957 )), L23359 ( HTBM1340 (ITS: PP736728; nrLSU: PP732958 )), L23360 ( HTBM1341 ) & L23361 ( HTBM1342 (ITS: PP736729; nrLSU: PP732959 )) ; same location, September 4, 2023, Jia Y. Lin, L 23380 ( HKAS133460 , partly isolated as HTBM1361 (ITS: PP736733; nrLSU: PP732963 )) ; China, Guangdong Province, Guangzhou City, Tianhe District, South China Agricultural University , Arboretum , on soil, 23°09’25”N 113°21’43”E, elevation 40 m, September 1, 2023, Jia Y. Lin, L 23377 ( HTBM1358 (ITS: PP736730; nrLSU: PP732960 )) ; same location, April 12, 2024, Kun L. Yang & Jia Y. Lin, K24023 ( HTBM1878 (ITS: PP736681; nrLSU: PP732911 )), K24024 ( HTBM1879 (ITS: PP736682; nrLSU: PP732912 )) & K24026 ( HTBM1881 (ITS: PP736683; nrLSU: PP732913 )) ; China, Guangdong Province, Guangzhou City, Tianhe District, South China Agricultural University , Qilin South Volleyball Court , on soil, 23°09’28”N, 113°22’10”E, elevation 20 m, April 3, 2024, Kun L. Yang & Hai-Feng Wu, K 24019 ( HKAS133462 , partly isolated as HTBM1874 (ITS: PP736674; nrLSU: PP732904 )) ; 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 24068 ( HTBM1942 (ITS: PP736684; nrLSU: PP732914 )) .

Additional notes: In the current phylogeny ( Fig. 2 ), the collections of this species resulted in three subclades with relatively distinct pairwise genetic distances. Both the ABGD and ASAP programs suggested our collections represent three separate cryptic species, each with significant support, but the PTP program did not support this delimitation. Considering that these programs did not result in a consistent delimitation and that significant and stable morphological differences between the collections in each subclade were not found, we treated our collections as belonging to a single species for the moment.

The morphology of our collections fits the protologue of X. erinaceus well. The only notable difference could be that our basidiospore length measurement, on average, is 0.46 µm higher than that in the protologue. In some cases, this could be a signal for the differentiation of cryptic species within a species complex. However, considering that no morphological characteristics were yet to be found for each of the three cryptic species of X. erinaceus identified from our collections, we believe that more collections of this group, especially those from the type locality ( India: Kerala), are needed to study before this taxon is split up.

This is the first report of X. erinaceus in China. It is common in Guangzhou, implying it should also be a common species in Asian regions with southern subtropical monsoon forests. However, to our knowledge, this is the second description of this species after its protologue in 1984.

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 5. Xanthagaricus chamaeleontinus (Photos by Zhen-Chao Liu, Kun L.Yang & Jia Y.Lin; drawings by Kun L.Yang & Jia Y. Lin, from HKAS133454 (holotype), HKAS133453 & HTBM0824). a–f. Basidiomata with violetish squamules on pileus (a–b. HKAS133451; c–e. HTBM0824; f. HKAS133453). g–i. Basidiomata with brownish squamules on pileus (HKAS133454 (holotype)). j–k. Basidiospores (j. Line drawing; k. SEM photo of HKAS133454 (holotype)). l. Hymenium and subhymenium. m. Cheilocystidia. n. Squamules at pileus center. o. Stipe squamules. Bars: a–i = 5 mm, j–m = 5 µm.

FIGURE 6. Xanthagaricus erinaceus (Photos by Jia Y. Lin & Kun L. Yang; drawings by Kun L.Yang & Jia Y. Lin, from HTBM1340). a– m. Basidiomata (a. HKAS133460; b. HTBM1342; c. HTBM1340; d. HTBM0941; e. HTBM0936; f–g. HKAS133459; h–i. HTBM1942; j. HTBM1313; k–l. HTBM1879; m. HKAS133462). n–p. Basidiospores (n. A typical grain with abundant warts under SEM, from HKAS133460; o.A nontypical grain with scarce warts under SEM, from HKAS133462; p. Line drawing).q.Hymenium and subhymenium. r. Cheilocystidia. s. Squamules at pileus center. t. Stipe squamules. Bars: a–b, d–g, m = 20 mm, c, h–l = 10 mm, n–o = 2 µm, p–r = 5 µm, s–t = 20 µm.