Distribution of gypsy sequences in Drosophila species of the obscura subgroup.

Eight Drosophila species of the obscura subgroup were screened for sequences homologous to the gypsy retrotransposon of D. melanogaster. Molecular characterization of gypsy sequences was first approached through digesting genomic DNAs from these obscura species with appropriate restriction enzymes and subjecting them to Southern blot analysis. The results of this analysis indicate that gypsy-homologous sequences are well conserved among species of the obscura subgroup. With the exception of D. guanche, all other species bear a 7 kb Xho I fragment that represents the complete element in D. melanogaster. Lower molecular weight fragments that could be deleted elements, are shared by different species. Both types of element probably existed before the divergence of this subgroup. Two different species clusters could be established on the basis of hybridization patterns, one represented by D. subobscura and its relative species D. guanche and D. madeirensis, and the other, in which D. obscura, D. tristis and D. subsilvestris are included.