Macropsalliota Kun L. Yang, Jia Y. Lin & Zhu L. Yang, 2024

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 : 228-229

Macropsalliota Kun L. Yang, Jia Y. Lin & Zhu L. Yang , gen. nov.

Registration identifier:— FN572131

Etymology:— Referring to the basidiomata, which are larger and more robust than those of its closely related genus Micropsalliota .

Type species:— Macropsalliota americana (Peck) Kun L. Yang, Jia Y. Lin & Zhu L. Yang (see below) (≡ Agaricus americanus Peck, Annual Report on the New York State Museum of Natural History 23: 71 (1872); ≡ Leucoagaricus americanus (Peck) Vellinga, Mycotaxon 76: 433 (2000))

Diagnosis:— Differing from its closely related genus Micropsalliota by usually more robust basidiomata, pileus with granular, fibrous, or flaky squamules composed of perpendicular to interwoven hyphae, whitish to yellowish lamellae, slightly colored basidiospores with a germ pore, and the different distribution range of the long continuous gap region in the ITS alignment with it.

General characteristics:— Basidiomata usually small to medium-sized, robust or moderately robust, turning yellowish, orangish, reddish to brownish after touched or damaged, becoming pinkish, reddish to purplish after dried. Pileus usually convex to plano-convex, more or less umbonate, with granular, fibrous or flaky, brownish squamules on a whitish background, with a plicate margin. Lamellae usually free, crowded, whitish to yellowish, 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, with minute squamules becoming more abundant downwards and nearly concolorous with the squamules on pileus. Annulus usually median to superior, moveable or almost unmoveable, with a flaring to spreading margin, easily broken. Odor usually fungal. Taste usually fungal.

Basidiospores usually more or less ovoid to amygdaliform and thick-walled, smooth, slightly colored, dextrinoid, with a germ pore. Basidia usually four-spored. Lamella trama seeming regular, subregular to trabecular. Cheilocystidia usually present, more or less rostrate to capitate. Pleurocystidia usually absent. Pileus squamules usually composed of perpendicular to interwoven hyphae. Clamp connections usually absent.

Habits and distribution:— Usually gregarious, weakly to strongly caespitose, saprotrophic on soil or deadwood, in forests, lawns, urban areas, and compost, mainly known from the tropical, subtropical, and temperate regions of the Northern Hemisphere.

Notes:— This genus is distinct in morphology and ITS sequence but is not significantly supported by phylogenetic analyses; see section Discussion for details.

New combinations:— The following new combinations are proposed based on the phylogenetic and/or morphological evidence. See below for details.