Taxonomic consideration of the Japanese red-cap Caesar's mushroom based on morphological and phylogenetic analyses

• The Japanese “Amanita hemibapha” corresponded morphologically and phylogenetically to the lectotype of A. caesareoides.
• Amanita hemibapha sensu stricto was phylogenetically distant from the Japanese entity.
• The Japanese red-cap Caesar's mushroom is A. caesareoides.

The Japanese red-cap Caesar's mushroom, “Tamagotake”, formerly identified as Amanita caesarea or A. hemibapha, was reevaluated taxonomically. The morphological characteristics of Japanese “A. hemibapha” specimens corresponded to the lectotype of A. caesareoides, but not to the isotype of A. hemibapha. Phylogenetic analysis of the internal transcribed spacer (ITS) region of the nuclear ribosomal RNA gene showed that Japanese “A. hemibapha” specimens formed a single clade with the lectotype of A. caesareoides, which were positioned adjacently to A. caesarea and A. jacksonii. A Thai A. hemibapha specimen, which corresponded morphologically to the isotype of A. hemibapha, was grouped with the Indian specimens and indicated a distant clade from A. caesareoides. Therefore, the Japanese red-cap Caesar's mushroom is A. caesareoides.