The delineation of species among strains assigned to Debaryomyces hansenii was examined using a gene genealogies-based approach in order to compare spliceosomal intron sequences found in four housekeeping genes (ACT1, TUB2, RPL31 and RPL33). This revealed four distinct groups of strains containing, respectively, D. hansenii var. hansenii CBS 767T, D. hansenii var. fabryi CBS 789T, Candida famata var. flareri CBS 1796T (the anamorph of D. hansenii var. fabryi CBS 789T) and Debaryomyces tyrocola CBS 766T, whose species status was no longer accepted. The sequence divergence between these groups, reaching in some cases over 20 %, unambiguously isolated the groups as separate taxa, leading to a proposal for the reinstatement of the originally described species D. hansenii CBS 767T and D. tyrocola CBS 766T. The variety D. hansenii var. fabryi was further subdivided into two taxa, Debaryomyces fabryi CBS 789T and Candida flareri CBS 1796T (previously C. famata var. flareri and Blastodendrion flareri). The comparison of intron sequences therefore exposed cryptic species whose phenotypic traits are not distinguishable from known species, but which have significantly diverged from the genetic point of view. Hence, we describe the new taxon Debaryomyces macquariensis sp. nov. CBS 5571T is related to, but clearly distinct from, the Debaryomyces species mentioned above. The approach used in this work has also revealed the existence of populations within the newly delineated species D. hansenii and genetic exchanges between these populations, indicating an unexpected genetic diversity within this part of the genus Debaryomyces.
https://www.ncbi.nlm.nih.gov/pubmed/19406826