A revision of the Inocybe grammata group in North America including four new taxa

A systematic revision of North American species with morphological similarities to Inocybe grammata was conducted based on materials collected in eastern and western North America and Central America. Eight taxa are confirmed in the group proposed here as I. sect. Albodiscae sect. nov., species of which are often characterized by a bicolorous pileus with a distinct pallid disc, the margin covered with superficial silky fibrils, entirely pruinose stipe with a slight or obvious marginate bulbous base, angular to angular-nodulose basidiospores with comparatively few nodules, and thick-walled cystidia. Species in the section are mainly distinguished by basidiome size, pileus color and texture, variation in basidiospore length and number of nodules, to some extent geographic location, and plant association. The section includes the widely distributed I. grammata (= I. albodisca), which associates with conifers and birch in eastern North America; I. albodiscoides sp. nov. from the Pacific Northwest, previously subsumed under I. grammata and I. albodisca; I. floridana from northern Florida, reported for the first time in more than 75 years; I. acriolens, an apparent associate of hemlock and pine in southeast Canada and the northeast U.S.; I. grammatoides, an aspen associate in northern regions of the U.S. and southeast Canada; I. velicopia sp. nov., a widely distributed associate of oak and chestnut in the eastern U.S. and Costa Rica; I. panamica sp. nov. from oak and oak-Oreomunnea (Juglandaceae) forests in Costa Rica and Panama; and I. vestalis, a European species sister to the rest of sect. Albodiscae but lacking the distinct bicolored pileus. Independent phylogenies of ITS+28S, rpb2, and rpb1 are inferred. Taxonomic descriptions, illustrations, and/or notes of the North American taxa are provided.