Amanita circulata Y.Y. Cui, Q. Cai and Zhu L. Yang
Fungal number: FN 571585.
Basidioma small to medium-sized. Pileus 3–7.5 cm diam., convex, plano-convex to applanate, umbonate; surface gray-brown (4E2–4) to dark brown (3F6–8) at center and margin, forming a distinctly pale colored [brown (3D2–4) to brownish (2C2–4)] ring-like zone at proximal end of marginal striations; volval remnants on pileus absent; margin striate (0.2–0.5 R), non-appendiculate; trama white (1A1), unchanging. Lamellae free, crowded, white (1A1); lamellar edges white (1A1); lamellulae truncate, plentiful. Stipe 9–18 cm long × 0.5–1.5 cm diam., slender, subcylindric, slightly tapering upwards, with apex slightly expanded, white (1A1), gray (1B1), brownish (2B2–4) to gray-brown (2C2–4); context white (1A1), hollow in center; basal bulb absent; volva saccate, membranous, both surfaces white (1A1). Annulus absent. Odor indistinct. Lamellar trama bilateral. Mediostratum 20–40 μm wide, composed of abundant, ellipsoid inflated cells (25–60 × 10–30 μm); filamentous hyphae abundant, 2–8 μm wide; vascular hyphae scarce. Lateral stratum composed of abundant, ellipsoid to fusiform inflated cells (20–40 × 10–25 μm), diverging at an angle of ca. 30° to 60° to mediostratum; filamentous hyphae abundant and 2–7 μm wide. Subhymenium 30–40 μm thick, with 2–3 layers of ellipsoid to fusiform or irregularly arranged cells, 5–10 × 5–10 μm. Basidia 45–60 × 15–20 μm, clavate, 4-spored; sterigmata 5–8 μm long; basal septa lacking clamps. Basidiospores [60/3/3] (10.5–) 11–13 (–13.5) × (9.5–) 10–12.5 (–13) μm, Q = 1–1.15 (–1.21), Qm = 1.08 ± 0.05, globose to subglobose, occasionally broadly ellipsoid, inamyloid, colorless, thin-walled, smooth; apiculus small. Lamellar edge appearing as a sterile strip, composed of subglobose to ellipsoid or sphaeropedunculate inflated cells (15–50 × 10–45 μm), single and terminal or in chains of 2–3, thin-walled, colorless; filamentous hyphae abundant, 2–6 μm wide, irregularly arranged or ± running parallel to lamellar edge. Pileipellis 50–90 μm thick; upper layer (15–40 μm thick) gelatinized, composed of radially arranged to interwoven, thin-walled, colorless, filamentous hyphae 2–5 μm wide; lower layer (35–50 μm thick) composed of radially arranged, filamentous hyphae 3–6 μm wide, colorless to brownish; vascular hyphae scarce. Interior of volval remnants on stipe base composed of longitudinally arranged elements: filamentous hyphae dominant and very abundant, 3–10 μm wide, colorless, thin-walled, branching, anastomosing; inflated cells rare, globose, subglobose, ellipsoid to fusiform, 50–80 × 40–50 μm, colorless, thin-walled, mostly terminal or sometimes in chains of 2–3. Outer and inner surface of volval remnants on stipe base similar to structure of interior part, but with inner surface gelatinized. Stipe trama composed of longitudinally arranged, clavate terminal cells, 80–250 × 15–40 μm; filamentous hyphae scattered to abundant, 2–10 μm wide; vascular hyphae scarce. Clamps absent in all parts of basidioma.
Habitat: Solitary to scattered on soil in subtropical mixed forests with Fagaceae and Pinaceae.
Distribution: known from eastern and southwestern China.
Additional specimens examined: CHINA. ANHUI PROVINCE: Huangshan, in a broad-leaved forest with trees of Fagaceae, altitude 620 m, 13 July 2018, Hong-Yu Chen 32 (HKAS 127629); same location, in a broad-leaved forest with trees of Fagaceae, altitude 610 m, 12 July 2018, Ting Guo 979 (HKAS 127639). YUNNAN PROVINCE: Baoshan, Tengchong, in a mixed forest with trees of Pinus, Quercus and Keteleeria, altitude 1900 m, 20 July 2009, Li-Ping Tang 858 (HKAS 56815); same county, in a forest with trees of Pinus armandii Franch. and Keteleeria fortune (A. Murray bis) Carrière, altitude 2010 m, 14 August 2010, Qing Cai 391 (HKAS 67955); same city, Changning County, forest type unknown, altitude 2000 m, 25 July 2009, Gang Wu 4 (HKAS 57535); Kunming, Panlong District, in a mixed forest with trees of Fagaceae and Pinaceae, altitude 1990 m, 21 August 2016, Xiao-Xia Ding 111 (HKAS 97054); same city, Wuhua District, in a mixed forest with trees of Fagaceae and Pinaceae, altitude 1990 m, 6 September 2012, Yan-Jia Hao 753 (HKAS 76411); Lincang, Fengqing County, in a mixed forest with trees of Fagaceae and Pinaceae, altitude 1800 m, 26 July 2009, Gang Wu 12 (HKAS 57543); Puer, Lancang Lahu Autonomous County, in a mixed forest with trees of Fagaceae and Pinaceae, altitude 1780 m, 29 September 2016, LC-LJW 280 (HKAS 97784); same county, in a forest dominated with trees of Fagaceae, altitude 1350 m, 31 August 2017, Zhu L. Yang 6049 (HKAS 101238).
Notes: Amanita circulata is somewhat related to A. flavidocerea. However, the latter can be easily distinguished from the former species by its non-umbonate pileus, which is yellow and lacks a ring-like zone at the proximal end of marginal striations. Amanita pallidozonata and A. zonata Y.Y. Cui et al. might be confused with A. circulata due to the pronounced ring-like zones at the proximal end of the marginal striations. However, A. pallidozonata differs from A. circulata by its more inflated cells in the inner part of volval remnants on the stipe base. Amanita zonata has relatively smaller basidiospores (9–10.5 × 8.5–10 μm).
Fig.1 Phylogenetic tree of sect. inferred from maximum likelihood analyses based on the combined dataset (nrLSU, and ). Bootstrap values over 50% and Bayesian posterior probabilities over 0.90 are shown along the branches. Sequences from type collections are indicated with (T), and new species are in boldface.