From chaos to tranquillity: a modern approach to the identification, nomenclature and phylogeny of Aspergillus, Penicillium and other Eurotiales, including an updated accepted species list

Eurotiales is a diverse and speciose order and includes economically important genera like Aspergillus, Penicillium, Paecilomyces and Talaromyces. Historically, species identifications based on morphology are challenging. The publication of accepted species lists and the availability of representative DNA sequences for type strains have contributed greatly towards accurate species identification and facilitated the description of many new species. However, despite current advancements, a proportion of newly described species within these taxonomically challenging genera represent, in fact, existing species, which raises obvious concerns. This study thus aimed to further modernise the taxonomy of Eurotiales by addressing key challenges in species identification and classification. Our study objectives were threefold: 1) to review species described after 2023, 2) update the accepted species list, and 3) release a curated DNA sequence dataset to facilitate future species identifications. We conclude that a move to a phylogenetic species concept is necessary but continue to support the inclusion of morphological descriptions and, where possible, associated secondary metabolite, exoenzyme, physiology and ecological data when introducing new species. Based on our phylogenetic analyses, we accept 130 of 171 species described since 2023 but reduce 41 to synonyms. Furthermore, we also reduced 17 species described pre-2023 to synonyms. Our list now contains 1393 species classified into four families and 26 genera, with Aspergilus (n = 465), Penicilium (n = 598) and Talaromyces (n = 236) containing the most species. To aid sequence-based identifications and species descriptions under a phylogenetic species concept, we release a curated DNA reference sequence database containing 18837 DNA sequences (3867 ITS, 5277 BenA, 5110 CaM and 4583 RPB2) generated from 5325 strains. Sequences were selected to best cover the infraspecies variation under our current understanding of each species. The species list and sequence database will be kept up to date as new information becomes available and will remain available at https://doi.org/10.5281/zenodo.16605949. This manuscript presents a major leap towards our goal to facilitate work with Eurotiales, while providing the taxonomic framework to support research excellence related to this important fungal group.