In order to reveal the mechanism for the high heterozygosity of an inversion on the left arm of the second chromosome, In(2L)B1D5, several pure lines were established of Drosophila albomicans for an esterase dimer locus (Est-F). This locus was shown to be eithe r inside the inversion region, or outside, but closely linked with it. By a chromosome extraction procedure, we have found that the Wulai D. albomicans population exhibits high heterozygosity (0.54) of the In(2L)B1D5 and that it also has a high frequency of recessive lethals (0.42), but low allelism. These genetic marker strains not only made the chromosome extract ion possible, but were used to reveal that the Wulai population is at linkage equilibrium, whereas the Chitou population is at linkage disequilibrium. A possible mechanism, accumulat ion of recessive lethals in the presence of a chromosomal inversion in a seasonally fluctu ating population, is proposed to explain the phenomena of high inversion heterozygosity, high lethal ity, and low allelism in the Wulai population.
Chromosomal inversion, Drosophila albomicans, Esterase, Lethality , Population genetics
