ALLELE-SPECIFIC POPULATION-STRUCTURE OF DROSOPHILA-MELANOGASTER ALCOHOL-DEHYDROGENASE AT THE MOLECULAR-LEVEL

The history of the Drosophila melanogaster alcohol dehydrogenase (ADH) Fast/Slow polymorphism was studied by recording molecular variation a nd inversion polymorphism in 233 chromosomes from European and African populations. Silent molecular variation in the Slow allele was very d ifferent between standard chromosomes and chromosomes bearing the In(2 L)t inversion. Within populations, inverted Slow haplotypes were more variable than standard Slow haplotypes. Between populations, geographi cal structure was almost nonexistent for inverted Slow haplotypes and highly significant for standard Slow. All Fast haplotypes occurred on standard chromosomes. They showed little variation within and between populations. They were highly significantly closer to standard Slow ha plotypes from Europe. These results suggest that the current range of Fast and In(2L)t Slow haplotypes is recent and that an older genetic d ifferentiation between populations was followed by allele-specific gen e flow.