Species in the Inocybe praetervisa group are characterized by producing nodulose to angular basidiospores and a bulbous, marginate, white stipe devoid of any pinkish to reddish tinge. Species delimitation problems and common misinterpretations in the I. praetervisa group have not yet been resolved through type studies and analysis of molecular data. This study seeks to clarify the taxonomy and nomenclature of species around I. praetervisa. Analyses of the nuc rDNA internal transcribed regions (ITS) recovered two major groups within the I. praetervisa group that can be separated on the basis of cystidial morphology. The study of three authentic and topotypic specimens in the Bresadola herbarium revealed that the name I. praetervisa has been misapplied often. The ITS region of one of the specimens was obtained, and this specimen is designated as epitype in support of a lectotype. Inocybe rivularis is demonstrated to be a later synonym of I. praetervisa, while Inocybe phaeocystidiosa is the correct name for the species most often misdetermined as I. praetervisa. Inocybe salicis-herbaceae and I. praetervisa var. flavofulvida are shown to be synonyms of I. phaeocystidiosa based on ITS sequence data from type collections. A new species sister to I. phaeocystidiosa with a Mediterranean distribution is described as I. praetervisoides. Cystidial morphology, distribution of caulocystidia, basidiospore morphology and ecology are shown to be the main diagnostic characters for separating the species. Inocybe praetervisa and I. phaeocystidiosa have a transoceanic distribution in Europe and North America, whereas I. praetervisoides so far is known only from the Mediterranean region.
Keywords: Agaricales; Inocybaceae; Inocybe phaeocystidiosa; barcoding; molecular taxonomy; systematics.
© 2016 by The Mycological Society of America.