Short-range genetic structure of Drosophila melanogaster populations in an Afrotropical urban area and its significance.
Alcohol dehydrogenase (Adh) (alcohol:NAD+ oxidoreductase, EC 1.1.1.1) gene frequencies and ethanol tolerance in Drosophila melanogaster are known to exhibit long-range latitudinal variations on different continents; this has led to the argument that the clines are adaptive. Accordingly, tropical populations are characterized both by a low frequency of Adh-F and by a low ethanol tolerance. In the urban area of Brazzaville (Congo) under an equatorial African climate, an original genetic structure of local populations has been found: Adh-F frequency varies from 3% to 90% when countryside and brewery populations are compared. This variation is accompanied by an increase of ethanol tolerance (from 6% to 13% alcohol). Such differences, which have remained stable for the past 3 years, were observed between collection sites less than 1 km apart. Two other enzyme loci exhibited a correlated variation with Adh-F--i.e., an increase of the S allele of glycerol-3-phosphate dehydrogenase (NAD+) (sn-glycerol-3-phosphate:NAD+ 2-oxidoreductase, EC 1.1.1.8) and of the F allele of glucose-6-phosphate dehydrogenase (D-glucose-6-phosphate:NADP+ 1-oxidoreductase, EC 1.1.1.49). Such observations suggest very strong selective pressures exerted by environmental ethanol that oppose the gene flow due to adult dispersal between contiguous habitats. A functional relationship between the polymorphisms of the three enzyme loci seems likely, and a metabolic interaction involving NAD and NADP cofactors is proposed.
Vouidibio
J
J
Laboratoire de Biologie Cellulaire, Faculté des Sciences, Brazzaville, R.P. Congo.
Capy
P
P
Defaye
D
D
Pla
E
E
Sandrin
J
J
Csink
A
A
David
J R
JR
D000483:Alleles; D000818:Animals; D003223:Congo; D003710:Demography; D004331:Drosophila melanogaster / Q000187:drug effects / Q000235:genetics*; D000431:Ethanol / Q000494:pharmacology; D005787:Gene Frequency; D005828:Genetics, Population; D005843:Geography; D005954:Glucosephosphate Dehydrogenase / Q000235:genetics; D005993:Glycerolphosphate Dehydrogenase / Q000235:genetics
D000431:Ethanol; D005993:Glycerolphosphate Dehydrogenase; D005954:Glucosephosphate Dehydrogenase