Phylogeny of the genus Kluyveromyces inferred from the mitochondrial cytochrome-c oxidase II gene

A phylogenetic analysis of 17 species belonging to the genus Kluyveromyces and 12 reference and outgroup species was performed using mitochondrial cyt ochrome-c oxidase Il gene sequences. The genus Kluyveromyces appears as a p olyphyletic taxon formed by species included within the following four main groups. The Kluyveromyces phaffii group encompasses the species Kluyveromy ces blattae, K, phaffii and Kluyveromyces yarrowii. The Kluyveromyces marxi anus group is a monophyletic group consisting of the species Kluyveromyces aestuarii, Kluyveromyces dobzhanskii, Kluyveromyces lactis, K. marxianus an d Kluyveromyces wickerhamii. The monophyletic Kluyveromyces thermotolerans group is formed by K. thermotolerans, Kluyveromyces waltii and Saccharomyce s kluyveri (which appears in the mitochondrial tree as the sister clade of the K. marxianus group). Finally, the Saccharomyces cerevisiae group contai ns the remaining Kluyveromyces species, as well as the reference Saccharomy ces species (sensu late and sensu stricto) and Candida glabrata (the phylog enetic relationships within this group are unclear according to the bootstr ap test). The phylogenetic relationships obtained for this mitochondrial ge ne are, for the most part, congruent with previous trees based on nuclear r RNA sequences, except for the position of K. yarrowii and the close relatio nship between the K. marxianus and K. thermotolerans groups. These differen ces, as well as the existence of these groups, are discussed in the context of previous studies based on phenotypic, genetic and molecular data. Altho ugh additional studies are required to decipher the phylogenetic relationsh ips between the genus Kluyveromyces and the closely related genera Saccharo myces, Torulaspora and Zygosaccharomyces, future changes to their taxonomic status should take account of the existence of these four groups of Kluyve romyces species.