Agaricus purpurlesquameus M.Q. He & R.L. Zhao.
Pileus 35 mm in diameter, convex, disc slightly truncate, background white, margin straight with appendiculate remains of universal veil; surface dry, covered by fibrillose scales, scales purple, triangular, appressed, extremely denser and thick at disc, scanty towards the margin. Context flesh, white. Lamellae up to 3 mm in diameter free, crowded, normal, white to pinkish brown, edge even. Annulus fragile, membranous, single, white, pendant, upper side smooth, lower side tomentose. Stipe 34 × 6–10 mm, white, hollow, cylindrical; surface dry, with white fibrils below the annulus. Odour of almond or aniseed. Basidiome become yellow when cutting and bruising. KOH reaction: positive yellow. Basidiospores 5.5–6.6 × 3.6–4.2 μm, (`x = 6.2 ± 0.3 × 3.9 ± 0.2, Q = 1.5–1.7, Qm = 1.5 ± 0.1, n = 20), ellipsoid, smooth, thick-walled, brown. Basidia 15.7–26.4 × 6.5–8.6 μm, clavate, hyaline, 4-spored, smooth. Cheilocystidia 19.0–33.6 × 9.9–15.6 μm, pyriform, with yellow pigments inside. Pleurocystidia absent. Pileipellis a cutis composed of hyphae of 4–7.5 μm in diameter, smooth, cylindrical, light brown, constricted at the septa.
Habitat: solitary on soil at road side.
Material examined: THAILAND, Mae Hong Son Province, 25 Sep 2016, M.Q He., (LE2016047, holotype, MFLU 17-1306).
Notes: The simple annulus, positive yellow KOH reaction and almond odour of the basidiome, confirm this new species is a member of subgenus Minores. Phylogeny analyses shows A. purpurlesquameus is a member of section Minores (Fig. 1). It has an identical ITS sequence with NT62/A. sp. (ITS: JF727845, Zhao et al. 2011), so we considered they are the same species. Agaricus purpurlesquameus is sister to A. patris but lacks statistic support. Compared with A. patris in morphology, both species has a purple pileus and a single annulus with tomentose lower surface. They differ in their cheilocystidia, in A. purpurlesquameus they are pyriform, while in A. patris are clavate to broadly clavate or sphaeropedunculate (Chen et al. 2017). Agaricus rufuspileus and A. sodalis are in the same clade with LE2016047, and they
can easily distinguished by basidiospores and cheilocystidia. The cheilocystidia of A. rufuspileus are clavate (He et al. 2017), while in A. purpurlesquameus they are pyriform. Agaricus sodalis have smaller basidiospores (`x = 5.4 × 3.6 μm) than A. purpurlesquameus. Agaricus purpurlesquameus is characterised by its purple pileus and pyriform cheilocystidia with yellow pigments.
Fig. 1 Maximum likelihood (ML) tree of Agaricus subg. Minores based on ITS sequences with the outgroup Agaricus rufoaurantiacus. The bootstrap support values greater than 50% and Bayesian posterior probabilities greater than 0.9 are indicated at the nodes (BS/PP). The branches with Bayesian posterior probabilities greater than 0.95 are in bold. New species are in bold
Fig. 1 continued