Mitochondrial DNA in the Drosophila melanogaster complex.

Mitochondrial DNA in the complex Drosophila melanogaster was among the first studied in metazoans. The variability of the molecule was extensively studied using restriction enzymes, gene sequence and recently sequence of the whole coding region. Within the complex, seven major haplotypes have been described, one (me) in D. melanogaster, three in D. simulans (siI, siII, siIII), two in D. mauritiana (maI, maII), and one in D. sechellia (se). The molecular distance between the haplotypes is comprised between 1 and 5%, except for siII and maI, which are virtually identical. The nucleotide diversity within each of these haplotypes is very low, varying from 0 to 0.0005. Most of the cytoplasms are infected by the bacterium Wolbachia and different bacterial strains infect cytoplasms harboring different mtDNA types. mtDNA polymorphism is discussed in relation with Wolbachia, nuclear polymorphism and speciation events.