Charting taxa in Amanita section Amidella (Basidiomycota: Amanitaceae)

Species determination in the Amidella clade is notoriously difficult, because of the relative dearth of diagnostic 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 (ncLSU, 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. At species level, around 81 clades were delimited, of which only 16–17 can be assigned a valid name, with a few more corresponding to provisional taxa listed in the amanitaceae.org website. Up to three 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 an infrasectional framework for optimising taxonomic sampling and designing clade-specific molecular markers to assist in identification.

Graphical Abstract