SEQUENTIAL GEL-ELECTROPHORETIC ANALYSIS OF ESTERASE-2 IN 2 POPULATIONS OF DROSOPHILA-BUZZATII

Sequential electrophoresis, using three different buffer systems on ce llulose acetate gels, was used to characterize the allelic variation f or esterase-2 in two populations of D. buzzatii in Australia that are separated by 550 km. Twenty-five alleles were detected, of which nine were unique to one population, eight unique to the other, and only eig ht were common to both populations. Allele frequencies within each pop ulation were significantly different between the two major chromosome sequences (standard and j inversion), and for each chromosome sequence allele frequencies were significantly different between populations. Observed allelic frequency distributions were not significantly differ ent from those predicted for selective neutrality using the homozygosi ty test statistic. However, estimates of the effective sizes of the po pulations derived from their observed differentiation, together with t he history of the species in Australia, provide support for some form of balancing selection affecting at least some of the alleles.