Repetitive DNA Components of the Large Hydromantes Genome: Phylogenetic and Molecular Aspects

We characterized four repetitive DNA families (Hsh 1, Hy/Pol III, Hsr 1, Hy500) in the lungless salamander Hydromantes (Amphibia: Urodela). These DNA components formed the basis for comparative studies of genome evolution; cloned repeats were used to study the conservation of these repeated DNA families among representative species of Hydromantes. Our molecular data support the close relationships among the European taxa and suggest an early evolutionary divergence between the European species of Hydromantes and their American relatives. Two of the DNA families that we characterized in Hydromantes (Hy/Pol III and Hsr 1) derive from two distinct RNA-mediated classes of transposable sequences. The high copy number of these sequences, as well as the nested and tandem arrayed organization observed in the Hy/Pol III units, suggest that retrotransposons are particularly important in shaping the large urodele genomes.