Isoenzyme frequencies in long-term selection lines of Drosophila melanogaster III. Isoenzyme frequencies of the esterases (Est) and larval alkaline phosphatases (Aph) in selection lines for short and long developmental rate.

1. A heterogeneous initial population which was founded by a double cross of four laboratory stocks was selected for developmental rates, two lines (KS and K) being selected for short developmental rate and two lines (LS and L) for long developmental rate. 2) After 88 to 183 generations of selection, frequencies of the Aph-D-alleles D(1), D(2), and D(0) and of the Est-6-alleles 6(F) and 6(S) were estimated by isoenzyme studies. 3) With the exception of the reference line RE, the allele Est-6(S) had been fixed. With the exception of the lines RE and LS, the allele Aph-D(2) had been eliminated. 4) In all lines the allele Aph-D(0) showed an almost constant frequency of about 0.197, only in line LS was the frequency much higher, at 0.265. 5) The selection had no clearly distinctive effect on the distribution of the Aph-D- and Est-6-alleles, since the same mode of selection resulted in different allele frequencies. 6) Selection restricts the degree of heterozygosity and the degree of allele polymorphism except for the Aph-D-alleles D(2) and D(o) in the line LS.