Re-assessment of the taxonomy of Antarctic mushrooms from King George Island, Antarctica

King George Island, one of the most rapidly warming regions in maritime Antarctica, has experienced pronounced expansion of ice-free areas and proliferation of cryptogamic vegetation in recent decades. This accelerated ecological greening has been accompanied by repeated reports of Arrhenia , Galerina , and Omphalina species. However, despite their frequent occurrence, comprehensive taxonomic assessments of these Antarctic mushrooms remain limited and unresolved. We applied an integrative systematic framework combining morphological examination, multilocus phylogenetic reconstruction, species delimitation analyses, and chemical analyses to 50 mushroom specimens collected from vegetated ice-free areas of King George Island. By integrating polyphasic evidence, we confirmed four species ( Arrhenia antarctica , Galerina fallax , Galerina venenata , and Omphalina frigida ) and resolved several historical taxonomic uncertainties related to these species. This study provides the first phylogenetic analysis of Arrhenia antarctica , a first mushroom species documented from Antarctica. Additionally, regarding Antarctic Omphalina , for which several new species have recently been reported from Antarctica, we verified that the real species diversity has been inflated and have rectified it. Lastly, LC-MS/MS analysis confirmed amanitin production in materials identified as Galerina pseudomycenopsis , thereby clarifying previous taxonomic ambiguity within the Galerina marginata species complex by synonymizing Galerina pseudomycenopsis with Galerina venenata . Divergence-time estimation further suggests that Antarctic lineages diversified before current climate warming, likely in association with repeated glacial-interglacial cycles that reshaped ice-free habitats in Antarctica. By clarifying species identities and integrating multilocus phylogenetics with temporal inference, this study revises the taxonomy of key Antarctic mushrooms and provides a robust framework for future investigation in their diversity, ecological roles, and potential adaptive mechanisms associated with Antarctic greening in extreme environments.