Mystagaricus, a new genus within the core Agaricaceae to accommodate Leucoagaricus brunneolilacinus described from a tropical greenhouse in Hungary

Tropical greenhouses provide unique environments for studying macrofungi, including lepiotoid taxa. One such enigmatic species, Leucoagaricus brunneolilacinus, was originally described from a subtropical greenhouse in Budapest, Hungary. However, its taxonomic position has remained uncertain due to conflicting classifications of Leucoagaricus and Leucocoprinus. To clarify its placement within the Agaricaceae family, we conducted morphological and multilocus phylogenetic analyses (ITS, LSU, RPB2, TEF1-α) using the type and recently collected specimens (including the here designated reference specimen) from greenhouses in Hungary and Austria. Our phylogenetic results reveal that L. brunneolilacinus does not cluster within either Leucoagaricus or Leucocoprinus, but instead forms a well-supported clade within the tribe Agariceae, alongside Pseudolepiota and Xanthagaricus. Based on these findings, we propose Mystagaricus as a new genus to accommodate this distinct lineage, with M. brunneolilacinus as the type species. Morphological traits such as a purplish brown, woolly pileus, dextrinoid and metachromatic basidiospores, and a unique pileus covering structure further support its generic distinctiveness. The species has only been recorded in greenhouses and a few outdoor sites in Europe and North America; its closest phylogenetic relatives originate from the Indo-China region, suggesting a yet undiscovered tropical natural habitat.