Amanita pseudoprinceps Y.Y. Cui, Q. Cai & Zhu L. Yang
Index Fungorum number: IF 824972
Basidioma medium-sized to very large. Pileus 8.5–16 cm diam., hemispherical, convex to applanate with age, light yellow (4A5–6) to greyish orange (5B3–4) or sometime golden yellow (5B7–8) at center, and becoming yellow white (4A2–3) to white (4A1) towards the margin; universal veil on pileus absent; margin striate (0.1–0.3 R), non-appendiculate; context 9.5–13.5 mm wide, white (1A1), unchanging. Lamellae free, crowded, white to cream white (1A1–2); lamellulae truncate. Stipe 11.5–17.2 × 1.1–1.9 cm, subcylindrical with slightly tapering upwards and apex slightly expanded, white, covered by minute, white (1A1) fibrous squamules; context fistulose to broadly fistulose, white (1A1), Bulb absent. Universal veil on stipe base saccate, membranous, up to 7 cm high, white (1A1). Partial veil apical, membranous, white (1A1), becoming fragile or disappear with age. Lamellar trama bilateral, divergent; mediostratum 40–75 μm wide, filamentous hyphae abundant, 2–12 μm wide; fusiform to ellipsoidal inflated cells 85–213 × 12–26 μm; vascular hyphae scarce to locally abundant. Subhymenium 30–50 μm thick in 2–3 layers, with subglobose to ellipsoidal or irregular cells, 12–33 × 10–26 μm. Basidia 36–53 × 12–18 μm, clavate, 4-spored with sterigmata 3–6 μm long; clamps present at base. Basidiospores (9.0–) 9.5–12.5 (–13.0) × (8.0–) 8.5–12.0 (–12.5) μm, Q = 1.00–1.20 (1.22) μm, Qm = 1.10 ± 0.06, globose to subglobose, sometimes broadly ellipsoid, inamyloid, hyaline, thin-walled, smooth; apiculus small. Lamellar edge sterile; filamentous hyphae 2–6 μm wide, hyaline, thin-walled; inflated cells, with subglobose to ellipsoidal, 12–35 × 8–34 μm, single and terminal or in chains of 2–3, hyaline, thin-walled. Pileipellis 85–160 μm thick; 2-layered, upper layer 45–80 μm thick, filamentous hyphae 2–5 μm wide, gelatinized, branching, thin-walled, hyaline; lower layer 40–80 μm thick, filamentous hyphae 2–8 (–15) μm wide, branching, thin-walled, hyaline to light yellow; vascular hyphae rare. Inner surface of universal veil on stipe base filamentous hyphae dominant 1–8 μm wide, hyaline to light yellow, thin-walled, branching; inflated cells, with subglobose, fusiform to clavate, 50–93 × 15–52 μm, hyaline, thin-walled, mostly terminal or sometimes in chains of 2–3; vascular hyphae rare. Outer surface of universal veil on stipe base similar to structure of inner part, but presenting more abundant inflated cells. Stipe trama longitudinally acrophysalidic; filamentous, undifferentiated hyphae 2–7 μm wide, thin-walled, frequently branching; acrophysalides 100–233 × 23–45 μm, thin-walled; vascular hyphae rare. Partial veil filamentous hyphae very abundant, 1–7 μm wide, hyaline, thin-walled; inflated cells scarce to locally anundant, globose, subglobose to ellipsoidal, 12–70 × 12–35 μm, hyaline to light yellow, thin-walled; vascular hyphae rare. Clamp connections present in all tissues of basidioma.
Habitat: Solitary to scattered on soil in tropical deciduous forests dominated by Dipterocarpus and Shorea.
Distribution: known from China and Thailand (this study).
Specimens examined: Thailand, Chiang Mai Province, Mae Taeng District, 19°05′38.2″ N 98°52′44.4″ E, alt. 1105 m, 7 August 2019, Yuan S.L., STO-2019-395 (SDBR-CMUSTO-2019-395); Yuan S.L., STO-2019-397 (SDBR-CMUSTO-2019-397); 19°07′45.0″ N 98°45′51.0″ E, alt. 1421 m, 9 August 2019, Yuan S.L., STO-2019-470 (SDBR-CMUSTO-2019-470); Yuan S.L., STO-2019-472 (SDBR-CMUSTO-2019-472). Doi Saket District, 18°53′2″ N 99°9′17″ E, alt. 343 m, 26 July 2020, Kumla J. and. Suwannarach N., CMUNK0783 (SDBR-CMUNK0783), 2 August 2022, Kumla J. and. Suwannarach N., CMUNK0853 (SDBR-CMUNK0853); Lumphun Province, Mae Tha District, 18°27′41″ N 99°10′30″ E, alt. 427 m, 25 July 2020, Kumla J. and. Suwannarach N., CMUNK0775 (SDBR-CMUNK0775).
Notes: Morphologically, A. pseudoprinceps resembles A. princeps Corner & Bas by having a similar yellowish-brown pileus and margin striates (about 0.2–0.3 R). However, A. princeps presents the larger basidiomata, as well as an outer layer of volval remnants on the stipe cracks and peels in pale buff thin patches. According to the phylogenetic analysis, our seven samples cluster together with three other samples of A. pseudoprinceps and form a well-supported clade that presents a sister clade with A. aporema Boedijn. Meanwhile, these two species possess a similar brown tone pileus. However, A. aporema has a smaller (6–10 cm) but much darker pileus, as well as obviously longer margin striates (0.5–0.6 R).
Fig. 1 The phylogenetic tree derived from maximum likelihood analysis of 64 specimens of the combined ITS, nrLSU, rpb2, and tef-1 genes. The tree is rooted with A. retenta and A. shennongjiana. Numbers above branches are the bootstrap percentages (left) and Bayesian posterior probabilities (right). Bootstrap values ≥ 75% and Bayesian posterior probabilities ≥ 0.90 are shown. The scale bar displays the expected number of nucleotide substitutions per site. Sequences derived in this study are shown in red. Type species are shown in bold.