Single-copy DNA relationships between diploid and tetraploid teleostean fish species

The degree of single-copy DNA relatedness among nine Salmonid, Osmerid, and Clupeid species (teleosts, order Isospondyli) was explored by interspecific DNA hybridization and the determination of the thermal stability of these hybrids. It is shown that the extent of base substitution and the amount of shared sequences is largely consistent with the systematic interrelationship of the species compared. A tentative estimate of the average base substitution rate is about 0.1-0.25% per million years, which is in the range typical for animal and plant nuclear genomes. The results are also discussed in view of the phylogenetically tetraploid state of the Salmonid genomes. A comparison of the amount of intra-genomic and inter-genomic divergence in the tetraploids suggests that a polyploidization event occurred recently in Salmonid evolution.