Charting Taxa in Amanita Section Amidella ( Basidiomycota : Amanitaceae )

Species determination in the Amidella clade is notoriously difficult, because of the relative dearth of field characters and the rather common occurrence of homoplasies. This results in a substantial number of misnamed and unnamed collections, a misapprehension of the geographic range of known species, and a gross underestimation of the number of species it contains. To assess the diversity that should be considered as part of Amidella , DNA sequences available for this group were retrieved in public nucleotide databases, using a combination of approaches to achieve a comprehensive representation. Phylogenetic analysis based on the aligned ITS sequences, consistently with the results from other molecular markers (nLSU, RPB2, TEF1, BTUB), suggests five major clades: one containing the type species Amanita volvata , another for Amanita ponderosa and allies, a third one (roughly half of all species) with Amanita lepiotoides , and two others without valid species yet. Consensus rRNA folding structures were obtained for these clades, maintaining their congruence and separation from neighbouring congeneric clades. At species level, around 78 clades were delimited, of which only up to 17 can be assigned a valid name, with a few more corresponding to provisional taxa listed in the amanitaceae.org website. Two further species without assigned sequences might correspond to the proposed clades. The current evidence suggests a rather narrow geographic range for most of these clades. This study provides a phylogeny-arranged outlook of the worldwide distribution of Amidella species, and a framework for designing clade-specific molecular markers to assist in identification.