MOLECULAR CHARACTERIZATION AND CYTONUCLEAR DISEQUILIBRIA OF 2 DROSOPHILA-SUBOBSCURA MITOCHONDRIAL HAPLOTYPES

According to restriction site analyses of mitochondrial DNA, Drosophil a subobscura shows a polymorphism that consists of two frequent haplot ypes that are evenly distributed all over the Old World and several ra re haplotypes never present in more than one locality. To ascertain th e causes responsible for such distribution, three different mtDNA frag ments from haplotypes I and II sampled in a population from Zurich hav e been partially sequenced. Only three silent nucleotide changes have been detected in the ND5 gene. One of them implies the loss of the Hae III restriction site, which differentiates haplotype I from haplotype II. On the basis of these results as well as on others involving the g eographic distribution of haplotypes I and II, they can be considered phenotypically equivalent. The sequencing study has been complemented with the analysis of cytonuclear disequilibria between mitochondrial h aplotypes and different nuclear loci in four D. subobscura populations . As expected, no significant cytonuclear disequilibria have been foun d between haplotypes I and II. Moreover, when haplotypes I and II were pooled and compared with the rare, endemic haplotypes similar results were obtained.