Taxonomic Revision of the pulcherrima Clade of Metschnikowia (Fungi): Merger of Species

Abstract

The type strains of 10 small-spored species of the ascomycetous yeast genus Metschnikowia usually form a compact group on the phylogenetic trees inferred from barcode sequences. Based on the name of the species, which was described first (Metschnikowia pulcherrima), the group is frequently referred to as the pulcherrima clade. All strains produce the iron-chelate pigment pulcherrimin and have antagonistic effects on many microorganisms. Recent results of molecular phylogenetic, genetic, and genomic research raised doubts about the taxonomic division of the clade. Those data—combined with results obtained in this study by comprehensive analysis of primary and secondary barcode sequences, physiological tests, and hybridisation experiments—demonstrate that the species cannot be distinguished from each other by the criteria of any of the phenotypic, phylogenetic, and biological species concepts. Therefore, I propose that the species of the pulcherrima clade be merged into one species under the oldest species name, M. pulcherrima.

Biocontrol potential of wine yeasts against four grape phytopathogenic fungi disclosed by time-course monitoring of inhibitory activities

“…All isolates matching to Metschnikowia pulcherrima- clade species were affiliated to Met. pulcherrima as proposed by Sipiczki, (2022) . Differentiation of Han.…”

Yeasts from tropical forests: Biodiversity, ecological interactions, and as sources of bioinnovation

“…Ephemeral flowers and their insects also yielded a small number of yeast species that were identified only by microscopy, for reasons of logistics. Noteworthy among these are M. reuukaufii , recognizable on the presence of characteristic bacilliform chlamydospores sometimes referred to as reukaufii cells, along with other Metschnikowia isolates that feature ovoid chlamydospores characteristic of species such as M. peoriensis (Kurtzman et al, 2018), M. pulcherrima (including several synonyms; Sipiczki, 2022), and a few others.…”

High intragenomic, intergenomic, and phenotypic diversity in pulcherrimin-producing Metschnikowia yeasts indicates a special mode of genome evolution

“…Recent analyses of the barcodes of the type strains of ten pulcherrimin-producing Metschnikowia species (grouped in the pulcherrima clade) found no clear barcode gaps between them due to very high intra-genomic (intra-strain) diversity of the sequences 5 , 6 . The intra-genomic sequence diversity is reflected in high numbers of “ambiguous nucleotides” (dimorphic, rarely polymorphic sites) in amplicon sequencing.…”

“…This phenomenon is rather unusual in yeasts and renders the determination of the taxonomic affiliation of strains and their differentiation from each other practically impossible. Because of the lack of clear barcode gaps the ten species of the clade were merged in one species under the taxonomic name M. pulcherrima 6 . However, the merged species is highly heterogeneous due the extremely high inter- and intragenomic primary barcode diversity.…”