The evolutionary history of Drosophila buzzatii. XXIII. High content of nonsatellite repetitive DNA in D. buzzatii and in its sibling D. koepferae

The frequency and types of repetitive nonsatellite DNA of two sibling species of the repleta group of Drosophila, D. buzzatii, and D. koepferae have been determined. For each species, the analysis is based on a sample of more than 100 clones (400 kb) obtained from genomic DNA. A theoretical model has been developed to correct for the presence of a mixture of repetitive and unique DNA in these clones. After correction, a high content of repetitive DNA has been demonstrated for both species (D. buzzatii, 19-26%; D. koepferae, 27-32%). The repetitive sequences have been classified according to their hybridization pattern when used as probes against genomic DNA and by their in situ hybridization signals on polytene chromosomes. Data suggest that the main nonsatellite component of these species is simpler and more repetitive than that of D. melanogaster, pointing to a wide variability in content and class size distribution of repetitive DNA among Drosophila species.