DISTRIBUTION OF GYPSY SEQUENCES IN DROSOPHILA SPECIES OF THE OBSCURA SUBGROUP

Eight Drosophila species of the obscura subgroup were screened for seq uences homologous to the gypsy retrotransposon of D. melanogaster. Mol ecular characterization of gypsy sequences was first approached throug h digesting genomic DNAs from these obscura species with appropriate r estriction 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 excepti on of D. guanche, all other species bear a 7 kb XhoI fragment that rep resents the complete element in D. melanogaster. Lower molecular weigh t fragments that could be deleted elements. are shared by different sp ecies. 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: