Contemporary documentation of the rare eastern North American species Inocybe insignis (Inocybaceae, Agaricales)

Inocybe insignis, an eastern North American species with greenish blue staining basidiomes, is documented for the first time since its original description circa 75 years ago in the Great Smoky Mountains. Here, we provide a detailed macroscopic and microscopic description and photographs of this rarely collected species, based on material collected in an Illinois oak-hickory forest. Analysis of molecular phylogenetic data strongly supports an evolutionary alliance with Asian and Australasian species of the Inocybe asterospora group. The combination of stellate basidiospores, marginate stipe base, entirely pruinose stipe, rimose pileus, and strong distinctive odor corroborates the molecular results, but the closest relatives of I. insignis lack the greenish blue staining characteristic of I. insignis.