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United States Department of Agriculture

Agricultural Research Service

Title: Current Issues in the Classification of Ascomycetous Yeasts - Generic Concepts in the Saccharomycetales

item Kurtzman, Cletus

Submitted to: Meeting Abstract
Publication Type: Other
Publication Acceptance Date: August 2, 2003
Publication Date: N/A

Technical Abstract: Many of the presently known ascomycetous yeast genera are defined from phenotype, but genus boundaries seldom correspond with those circumscribed from phylogenetic analysis of gene sequences. What is a phylogenetically defined genus? Briefly, this is a group of species genetically separated from other groups of species. Major questions at present are how much genetic separation should there be between groups or clades, and should phenotypic similarity be expected among members of a phylogenetically defined genus? Impacting on these questions is the issue of missing taxa, i.e., undiscovered species, and if they were present, what shape would they impart to a phylogenetically circumscribed genus. It is likely that we know only 1% or less of extant species, so even phylogenetically circumscribed genera will be "moving targets" well into the future. Multigene analyses of the "Saccharomyces complex" indicate that resolution of genera ordinarily requires the combined phylogenetic signal from several genes. Of the 13 phylogenetically defined genera detected in the "Saccharomyces complex," about half can be easily recognized from phenotype. Most of these genera have relatively few species. However, the Pichia membranifaciens clade appears to be a natural group, and if so, it will represent a genus with 20-30 known species.

Last Modified: 4/22/2015
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