Aureoboletus microcarpus N. K. Zeng, Xu Zhang & S. Jiang 2022, sp. nov.
Creators: name: Zhang, Xu
name: Tian, Run
name: Tang, Li-Ping
name: Liang, Zhi-Qun
name: Zhang, Wen-Hao
name: Jiang, Shuai
name: Wang, Cheng-Kai
name: Zeng, Nian-Kai
Publisher: name: Zenodo
Year: 2022
Subjects: Biodiversity
Taxonomy
Fungi
Basidiomycota
Agaricomycetes
Boletales
Boletaceae
Aureoboletus
Aureoboletus microcarpus

description: Aureoboletus microcarpus N.K. Zeng, Xu Zhang & S. Jiang, sp. nov. (Figs. 3C – D, 5)
MycoBank: MB841621
Etymology:—Latin “ microcarpus ” refers to the small basidiomata of the new species.
Diagnosis:—Differs from other species of Aureoboletus by a very small and glutinous basidioma, a dull reddishbrown, violet brown pileal surface, a pileal margin usually with white to subhyaline veil remnants when young, cylindrical basidiospores, and an ixotrichoderm-type pileipellis.
Holotype:— CHINA. Hainan Province: Yinggeling of Hainan Tropical Rainforest National Park, elev. 550 m, 7 July 2020, N. K. Zeng 4468 (FHMU4688). GenBank accession number: 28 S = OK327017, ITS = OM 200341, RPB2 = OM 280449.
Description:— Basidiomata very small-sized. Pileus 0.4–1.9 cm in diam., subhemispherical when young, then broadly convex to plane; margin usually with white (1A1) to subhyaline veil remnants when young; surface viscid, distinctly wrinkled, brown (6D3) to blackish brown (6E3); context 0.1–0.2 cm thick in the center of the pileus, white (1A1), unchanging in color when cut. Hymenophore poroid, adnate or slightly decurrent; pores approximately 0.5 mm in diam., subround, yellowish (1A3), unchanging in color when cut; tubes 0.1–0.3 cm long, pale yellow (1A6), unchanging in color when cut. Stipe 1.5–2.2 × 0.1–0.3 cm, central, subcylindrical, solid; surface yellowish-white (1A3), usually covered with a mucilaginous layer; context white (1A1), unchanging in color when cut. Basal mycelium white (1A1). Odor indistinct.
Basidia 22–30 × 7–10.5 μm, clavate, thin-walled, 4-spored, hyaline or yellowish in KOH; sterigmata 3–4 μm long. Basidiospores [150/3/3] 8.5–12.5(–13) × 4–5.5 μm, Q = (1.87–)2–2.77(–3), Qm = 2.4 ± 0.26, cylindrical, smooth, moderately thick-walled (up to 1 μm), yellowish brown (3B8) in KOH. Cheilocystidia 24–36 × 8–13 μm, fusoidventricose, moderately thick-walled (up to 1 μm), yellowish-white (1A3) or hyaline in KOH. Pleurocystidia 25–44 × 10–14 μm, subfusiform or fusiform, thin-walled, yellowish-brown (3B8) in KOH. Hymenophoral trama bilateral, composed of hyphae 3–8 μm wide, moderately thick-walled (up to 1 μm), yellowish (1A2) in KOH. Pileipellis an ixotrichoderm 200–300 μm thick, embedded in a gelatinized matrix, made up of hyphae 4–8 μm wide, moderately thick-walled (up to 1 μm), yellowish-white (1A3) or hyaline in KOH; terminal cells 26–39 × 4.5–8 μm, narrowly clavate or subcylindrical, with obtuse apex. Pileal trama composed of hyphae 3–8 μm wide, moderately thick-walled (up to 1 μm), hyaline in KOH. Stipitipellis a hymeniderm 300–500 μm thick, embedded in a gelatinized matrix, made up of hyphae 4–5 μm wide, moderately thick-walled (up to 1 μm), yellowish-white (1A3) or hyaline in KOH; terminal cells 25–43 × 4–5 μm, subclavate, subcylindrical, or subfusiform, with obtuse apex. Stipe trama made up of parallel hyphae 4–10 μm wide, thin- to slightly thick-walled (up to 0.5 μm), hyaline in KOH. Clamp connections not observed in any tissue.
Habitat:—Solitary on the ground in forests dominated by fagaceous trees (Lithocarpus spp.).
Known distribution:—Southern China (Hainan Province).
Additional specimen examined:— CHINA. Hainan Province: Yinggeling of Hainan Tropical Rainforest National Park, elev. 550 m, 3 July 2020, N.K. Zeng4465 (FHMU4722); same location and date, N.K. Zeng4467 (FHMU4695).
Notes: Phylogenetically and morphologically, A. microcarpus is closely related to A. glutinosus Ming Zhang & T.H. Li (2019: 121), A. marroninus T.H. Li & Ming Zhang, and A. tenuis T.H. Li & Ming Zhang (2015: 182) (Fig. 2). However, A. glutinosus, originally described from Hunan Province, central China, has a reddish-brown to ruby pileal surface usually with irregular reticulations and darker folds, and longer basidiospores [(9.5–)10–13.5 × (4–)4.5–5 μm] (Zhang et al. 2019); A. marroninus, firstly described from Guangdong Province, southern China, has a darker (violet brown or maroon) pileal surface, a context often slightly changing to blue, especially in the lower portion of the stipe when exposed, and smaller basidiospores [(8–)8.5–10 × 4–4.5(–5) μm] (Zhang et al. 2015); A. tenui s, originally described from Guangxi Province, southern China, has a larger pileus (2–3.5 cm in diam.), a wrinkled to shallowly reticulate pileal surface, an absence of appendiculate veil remnants, and a greyish-red to brownish-orange stipe (Zhang et al. 2014). Moreover, the phylogenetic distance is 0.167 between our new species A. microcarpus and its sister taxon A. glutinosus (Fig. 2), which falls within the range of values of 0.012 to 0.42 for the inter-specific variation of Aureoboletus species.
description: Published as part of Zhang, Xu, Tian, Run, Tang, Li-Ping, Liang, Zhi-Qun, Zhang, Wen-Hao, Jiang, Shuai, Wang, Cheng-Kai & Zeng, Nian-Kai, 2022, Morphological and phylogenetic evidence reveal three new species of Aureoboletus (Boletaceae, Boletales) from China, pp. 127-148 in Phytotaxa 567 (2) on pages 140-141, DOI: 10.11646/phytotaxa.567.2.2, http://zenodo.org/record/7141696