A comparison of interfertility and in vitro DNA-DNA reassociation as criteria for speciation in the genus Kluyveromyces.

Hybridization studies based on the use of the prototrophic selection technique were undertaken to compare interfertility and DNA-DNA reassociation as criteria for speciation purposes in the yeast genus Kluyveromyces. Degrees of DNA-DNA reassociation greater than 70% between strains, as reported in the literature, were found to correlate with high recombination frequencies. Degrees of DNA-DNA reassociation less than 20% between strains did, however, not invariably coincide with the absence of interfertility between strains. If interfertility is accepted as criterion for conspecificity, the hitherto reported low degrees (less than 20%) of DNA-DNA reassociation in Kluyveromyces cannot confidently be employed for speciation purposes.