Leucoagaricus Locq. ex Singer, 1948

Yang, Kun L., Lin, Jia Y., Li, Guang-Mei, Li, Taihui & Yang, Zhu L., 2024, Rediscovering Leucoagaricus sinicus, with the recognition of Leucoagaricus and Leucocoprinus as separate genera, and two new genera in Agaricaceae (Basidiomycota), Phytotaxa 676 (3), pp. 199-255 : 231-232

Leucoagaricus Locq. ex Singer , Sydowia 2(1–6): 35 (1948)

= Sericeomyces Heinem. , Bulletin du Jardin Botanique National de Belgique 48(3–4): 401 (1978) Type species:— Leucoagaricus rubrotinctus (Peck) Singer , Sydowia 2(1–6): 36 (1948) (≡ Lepiota rubrotincta Peck, Annual Report on the

New York State Museum of Natural History 44: 179 (1891); ≡ Leucocoprinus rubrotinctus (Peck) Redhead , Index Fungorum 551:

1 (2023))

Diagnosis:— Differing from the similar genus Leucocoprinus by usually producing slender to moderately robust basidiomata without a distinct color change after touched, damaged, or dried, non-plicate to shortly plicate pileus without or with squamules composed of horizontal to interwoven hyphae, basidiospores without a germ pore, saprotrophic in forests, and not symbiotic with attine ant species.

General characteristics:— Basidiomata usually small to medium-sized, slender to moderately robust, without a distinct color change after touched, damaged, or dried. Pileus usually convex to plano-convex, more or less umbonate, smooth or with fibrous or flaky, white or variously colored squamules on a whitish background, with a non-plicate to shortly plicate margin. Lamellae usually free, crowded, whitish, with a more or less cystidiose edge, interspersed with abundant lamellulae. Stipe usually more or less curved, subcylindrical, more or less bulbous at the base, whitish, smooth or with minute squamules. Annulus usually superior or median, almost unmoveable, with a flaring margin, easily broken. Odor usually fungal. Taste usually fungal.

Basidiospores usually more or less ovoid to amygdaliform and thick-walled, smooth, colorless, dextrinoid, without a germ pore. Basidia usually four-spored, monomorphous. Lamella trama regular, subregular to trabecular. Cheilocystidia usually present, sometimes with crystals on the apex. Pleurocystidia usually absent. Pileus squamules usually composed of horizontal to interwoven hyphae. Clamp connections usually absent in most tissues.

Habits and distribution:— Usually gregarious, not or weakly caespitose, saprotrophic on soil in forests, mainly known from the subtropical and temperate regions.

Notes:— In the current concept, Leucoagaricus is a significantly supported monophyletic group ( Figs. 1 & 2 ) restricted to the old concepts of Leucoagaricus sect. Rubrotincti and Sericeomyces , with the exception of the group of species around S. sericifer (in Leucocoprinus in the current concept). Urrea-Valencia et al. (2023) actually generated a similar phylogeny based on ITS and nrLSU data.

Schultz et al. (2024) explored the phylogeny of Agaricaceae s. str. members cultivated by attine ant species, based on 625 loci. All the collections classified as Leucoagaricus species in that study are currently recognized as Leucocoprinus species in this study, implying that no Leucoagaricus species in the current concept have known to be cultivated by attine ant species at the present stage.

New combination:— The following new combination is proposed based on the phylogenetic and morphological evidence. See below for details.

Figures

FIGURE 1. Overview of the five phylogenies based on different datasets; each genus with more than one collection inferred as a monophyletic group, and the outgroup is each collapsed as a triangle; nodes are annotated if supported by ≥50% MLB or ≥0.9 BPP; holotypes and paratypes are indicated by HT, and PT, respectively. A. Main phylogeny, inferred from the concatenated ITS-nrLSU-rpb2- tef-1α dataset with 392 collections, 313 of which do not have rpb2 and tef-1α sequences; see Fig. 2 for details. B. Phylogeny S1, inferred from the concatenated ITS-nrLSU-rpb2-tef-1α dataset with 68 collections, 61 of which have three to four loci. C. Phylogeny S2, inferred from the concatenated ITS-nrLSU dataset with 392 collections. D. Phylogeny S3, inferred from the concatenated rpb2-tef-1α dataset with 48 collections, all have both rpb2 and tef-1α sequences. E. Phylogeny S4, inferred from the concatenated ITS-nrLSU-rpb2-tef-1α dataset with 134 collections representative for Agaricaceae s. l.

FIGURE 2. Details of the Main phylogeny, inferred from the concatenated ITS-nrLSU-rpb2-tef-1α dataset. 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. Each genus is highlighted with a background color. Holotypes, isotypes, paratypes, and epitypes are indicated by HT, IT, PT, and ET, respectively; note that the paratypes of a species are only indicated when its holotype is not present.