Esterase 6 and reproduction in Drosophila melanogaster.

A nonspecific carboxylesterase (esterase 6) of Drosophila melanogaster shows greater activity in adult males than in females and is highly concentrated in the anterior ejaculatory duct of the reproductive tract of the male. Esterase 6 is depleted in males by copulation and is transferred to females early during copulation as a component of the seminal fluid. That esterase 6 may be involved in a system controlling the timing of remating is suggested by differences in the activity of this enzyme in a strain of Drosophila selected for a decrease in time to remating and by differences in the timing of remating in females initially inseminated by males lacking or having active esterase 6.

Modes of Selection Maintaining an Inversion Polymorphism in DROSOPHILA PAULISTORUM.

The possibility that fitness relationships associated with an inversion polymorphism in D. paulistorum were frequency dependent was investigated. Using allozymes of tetrazolium oxidase to mark inversions, the effects of genotype frequency, larval density, and culture conditions on fitness were assessed. The proportions of genotypes among egg-laying females were varied, thus changing the expected proportions of progeny produced in the absence of fecundity or viability selection. The genotypes of progeny were determined by electrophoresis and comparisons of the ratio of the numbers of the different genotypes produced to the expected ratio was used to evaluate fitness relationships. Fitness relationships were dependent on genotype frequency, larval density, and culture conditions. Selection was either absent, directional, frequency dependent (favoring rare types), or heterotic depending on density and culture conditions. It is implied that the adaptive value of genetic variants need not be apparent in all environments, or may change with changing conditions. There is evidence for different criteria for selection in the two sexes. These results add to the evidence supporting the importance of frequency-dependent selection. It is argued that for frequency dependence to be of general importance, selection must act on genes in groups, either as an inversion or as lengths of chromosome with integrity maintained by disequilibrium.

Quantitative genetic analysis of courtship and reproduction in female Drosophila melanogaster.

Three hundred mother-daughter pairs were analyzed for seven attributes related to courtship and reproduction. Only the lag time from first courtship to copulation was significantly heritable; genetic correlations involving this attribute were not significant. The genetic correlation between fertility and lag time to first courtship was negative and significant. However, this genetic correlation is expected to have little impact on the retention of additive genetic variance or on response to selection because it involves two attributes with low heritabilities. The pattern of phenotypic covariation among traits is largely explained by environmental causes and is consistent with that found in a previous analysis of father-son pairs (Gromko, 1987).

Genetic basis for remating in Drosophila melanogaster. IV. A chromosome substitution analysis.

Drosophila melanogaster lines previously selected for fast and slow return of female receptivity were subjected to a chromosome substitution analysis. Chromosomal effects on direct response to selection were distinctively different between selection lines derived from two different base populations. All three chromosomes tested affect the trait in the JEFFERS selection lines. In contrast, only chromosome II was found to have a main effect in the COMP selection lines. Significant interactions between chromosome II and the other chromosomes were also found in both of the selection lines. All of the components of virgin fly mating behavior measured were affected by chromosome II.

Genetic basis for remating in Drosophila melanogaster. V. Biometrical and planned comparisons analyses.

Drosophila melanogaster lines previously selected for fast and slow return of female receptivity were crossed to produce 16 lines (2 parental, 2 F1, 4 F2, and 8 backcross lines). Several genetic hypotheses could be tested both through particular planned comparisons among these 16 crosses and with a biometrical analysis. Both analyses identified the difference between the fast and the slow remating speed in these lines as having an autosomal basis. This is in agreement with observations from previous chromosome-substitution analyses. However, the planned comparisons yielded no significant deviations from expectations based on no dominance, no X-chromosomal factors, and no permanent cytoplasmic factors, whereas the biometrical analysis yields the best fit when some of these factors are included.

Genetic basis for remating in Drosophila melanogaster. VI. Recombination analysis.

Drosophila melanogaster lines previously selected for fast and slow return of female receptivity were used for two different recombination analyses. Major loci affecting the difference between the fast and the slow remating speed map to the right arm of chromosome II to the right of welt (wt).