The Inocybe geophylla group in North America: a revision of the lilac species surrounding I-lilacina

The Inocybe geophylla group is circumscribed based on phylogenetic analysis of DNA sequences largely sampled from North America and Europe. Twenty-nine phylogenetic species are uncovered after analysis of combined nuc 28S rDNA (28S) and RNA polymerase II second largest subunit (rpb2) DNA sequence data. Species in the I. geophylla group share the presence of a cortina, silky-fibrillose pileus and stipe, pruinose stipe apex, spermatic odor, thick-walled hymenial cystidia, and smooth amygdaliform or elliptical basidiospores. Within the group, as many as five phylogenetic species attributable to I. lilacina and allies form a strongly supported clade based on analysis of nuc ITS1-5.8S-ITS2 rDNA (ITS [internal transcribed spacer]), 28S, and rpb2 data. However, all lilac-colored species do not form a monophyletic group. Sufficient morphological and ecological data are present to document four of the I. lilacina subgroup species, two of which are described from North America as new: I. ionocephala and I. sublilacina. Inocybe lilacina is recircumscribed based on sequencing the holotype and is distributed in the eastern United States under pines and/or hardwoods. Inocybe pallidicremea is a widespread and common conifer associate in mostly northern parts of North America, to which the name I. lilacina was previously applied. Descriptions, photographs, line drawings, and a taxonomic key to lilac species in the I. lilacina subgroup from North America are provided. Well-documented collections, especially notes on gross morphology and ecology, are needed to continue to assess and describe the high taxonomic variation in the I. lilacina subgroup and its allies worldwide.