On the basis of detailed morphological and molecular investigation, eighteen new species of Inocybe (I. alberichiana, I. beatifica, I. bellidiana, I. clandestina, I. drenthensis, I. dryadiana, I. gaiana, I. ghibliana, I. grusiana, I. knautiana, I. lampetiana, I. oetziana, I. orionis, I. plurabellae, I. rivierana, I. scolopacis, I. sitibunda and I. tiburtina) are described. All of them are smooth-spored, and most of them are pruinose only in the apical part of the stipe. The new species are compared to 40 type specimens, all of which are described here and for several of which (partial) ITS sequences have been generated. For eight species, epi-, lecto- or neotypes were selected, among these are I. geophylla, I. glabripes and I. tigrina. Based on these studies, we suggest twelve synonymies, i.e. that I. clarkii is synonymous with I. sindonia, I. conformata with I. cincinnata, I. elegans with I. griseolilacina, I. fuscidula with I. glabripes, I. griseotarda with I. psammobrunnea, I. obscurella with I. obscuroides, I. obscuromellea with I. semifulva, I. patibilis and I. tigrinella with I. tigrina, I. petroselinolens with I. tenuicystidiata and I. rubidofracta with I. pseudorubens and I. subporospora is synonymized with I. tjallingiorum. All of the new species are supported by phylogenetic analyses. Among the previously described species accepted here, sixteen are represented by types in the phylogenetic analyses and ten by own collections morphologically corresponding to the type. In summary, we here verify or provide morphological concepts associated with molecular data for 44 smooth-spored species of Inocybe.

Nomenclatural type definitions are one of the most important concepts in biological nomenclature. Being physical objects that can be re-studied by other researchers, types permanently link taxonomy (an artificial agreement to classify biological diversity) with nomenclature (an artificial agreement to name biological diversity). Two proposals to amend the International Code of Nomenclature for algae, fungi, and plants (ICN), allowing DNA sequences alone (of any region and extent) to serve as types of taxon names for voucherless fungi (mainly putative taxa from environmental DNA sequences), have been submitted to be voted on at the 11th International Mycological Congress (Puerto Rico, July 2018). We consider various genetic processes affecting the distribution of alleles among taxa and find that alleles may not consistently and uniquely represent the species within which they are contained. Should the proposals be accepted, the meaning of nomenclatural types would change in a fundamental way from physical objects as sources of data to the data themselves. Such changes are conducive to irreproducible science, the potential typification on artefactual data, and massive creation of names with low information content, ultimately causing nomenclatural instability and unnecessary work for future researchers that would stall future explorations of fungal diversity. We conclude that the acceptance of DNA sequences alone as types of names of taxa, under the terms used in the current proposals, is unnecessary and would not solve the problem of naming putative taxa known only from DNA sequences in a scientifically defensible way. As an alternative, we highlight the use of formulas for naming putative taxa (candidate taxa) that do not require any modification of the ICN.

Twelve new species of Inocybe (I. adorabilis, I. comis, I. demetris, I. filiana, I. galactica, I. morganae, I. othini, I. ovilla, I. proteica, I. somae, I. suryana and I. venerabilis) are described from Europe on the basis of detailed morphological and molecular investigation. A portrait of the recently described I. ianthinopes is given. All species are smooth-spored and some pruinose only in the apical part of the stipe, and some on entire length. The new species are compared to 24 type specimens (17 characterized by at least partial ITS sequence data), all of which are described and revised here. Epitypes were selected for two species, I. hirtella and I. sindonia. Based on our studies, we confirm that I. kuehneri and I. sindonia on one hand, and I. subalbidodisca and I. ochroalba on the other, are synonyms and furthermore suggest that I. abietis is synonymous with I. catalaunica, I. exilis with I. rufobrunnea, I. hirtellarum with I. mycenoides, I. lapidicola with I. deianae, I. ochraceolutea with I. sindonia, I. stangliana with I. pelargonium, I. subrubens with I. subhirtella and I. sulfovirescens with I. langei. All of the new species are supported by phylogenetic analyses. Among the 16 previously described species accepted here, 10 are represented by types in the phylogenetic analyses and five by own collections corresponding to the type. Two species, I. eutheloides (remaining doubtful) and I. pallidolutea are only treated morphologically. In summary, we describe as new or verify the taxonomic status and provide or corroborate morphological concepts for 37 smooth-spored species of Inocybe.

Based on detailed morphological and genetic investigation, 11 new species of Inocybe (I. abdita, I. alcis, I. carissima, I. cryptica, I. culicis, I. mecoana, I. mortenii, I. orioli, I. rangiferi, I. sepiana and I. turfae) are described. Six of the new species are smooth-spored and five are nodulose-spored. The new species are compared to 18 type specimens, all of which are described here and for seven of which (partial) ITS sequences have been generated. For six species, namely I. griseovelata, I. lacera, I. soluta, I. subcarpta, I. tarda and I. transitoria, a lectotype, epitype or neotype was selected, and a description and a figure plate are provided for each of them. Based on our studies, we are convinced that I. albofibrillosa and I. striatorimosa are synonymous with I. soluta, while I. aurantioumbonata is synonymous with I. tarda. Furthermore, we affirm that I. longicystis is synonymous with I. stellatospora. All of the new species are supported by phylogenetic analyses. In summary, we here describe as new, verify the taxonomic status of, or provide or corroborate morphological concepts for 29 species of Inocybe.

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