Revisiting the Monascus genus (Eurotiales, Aspergillaceae): A Multilocus Phylogenetic Approach to Species Delimitation

Monascus spp. are economically important filamentous fungi that have been utilized in the production of beneficial metabolites such as Monascus pigments and monacolin K, as well as in the brewing of some Asian fermented foods. The delimitation of Monascus species has traditionally relied on phenotypic traits; however, this morphological classification approach is susceptible to subjective judgments and variations in cultural conditions and also may not necessarily be related to the actual genetic relationship. Consequently, synonymy and misidentification frequently occur in Monascus taxonomy, highlighting the urgent need for a convenient and reliable classification system for this genus. In this study, a phylogenetic analysis of 82 representative Monascus strains, encompassing all previously recognized species of the genus, was conducted based on the concordance of five gene genealogies (BenA, CaM, ITS, LSU, and RPB2) to clarify species delimitation and resolve phylogenetic relationships within Monascus. The results revealed that the genus Monascus is resolved into 11 species, which are clustered into two sections: Floridani (including M. argentinensis, M. flavipigmentosus, M. floridanus, M. lunisporas, M. mellicola, M. pallens, and M. recifensis) and Rubri (including M. pilosus, M. purpureus, M. ruber, and M. sanguineus). M. pilosus and M. sanguineus were reaffirmed as distinct species due to their well-supported and divergent phylogenetic lineages. Additionally, M. albidulus, M. anka, M. barkeri, and M. fumeus are synonymized with M. pilosus, while M. aurantiacus and M. rutilus are synonyms of M. purpureus. Finally, a comprehensive list of accepted Monascus species along with their corresponding barcode sequence data is provided.