[DNA-DNA hybridization in several species of Hansenula]

The genus Hansenula was considered a long time ago as a good pattern for phylogenetic research. In 1969, Wickerham proposed an evolutive scheme based upon morphological, physiological and ecological criteria. Recently, relatedness among yeasts were analysed by DNA-DNA hybridization in liquid medium. H. anomala var. anomala (G + C content: 37.1%) was compared with H. anomala var. schneggii (37.6%), H. subpelliculosa (33.8%) line 3, H. sydowiorum (40.1%) and H. muscicola (37.1%). These results showed little relatedness between H. anomala var. anomala/H. ciferrii and H. anomala var. anomala/H. subpelliculosa. On the other hand, H. anomala var. schneggii shared 89.5% of its nucleotide sequences with H. anomala var. anomala. These 2 strains were considered to represent the same species. H. holstii showed 67.1% complementarity with H. anomala var. anomala: this strain is considered to represent valid species, different from H. anomala var. anomala, but H. muscicola with 72.5% relatedness to H. anomala var. anomala could be considered as a 'limit species'. An unexpected finding was that H. beckii was closely related to H. anomala var. anomala (84.8%). These data suggested the inadequacy of current criteria used to establish the phylogenetic lines in genus Hansenula.