Minority mating advantage of certain eye color mutants ofDrosophila melanogaster. III. Female discrimination and genetic background

A repetition of certain experiments done 2 years previously with two eye color mutants,brown andscarlet, inDrosophila melanogaster was undertaken to reconfirm results; however, initial tests revealed that strains or conditions had changed so that females were less discriminating. Testing was undertaken with changes in genetic background and certain laboratory conditions, with single females courted by equal numbers of two eye color types of males (3 red,R: 3 orange,O). These eye colors were produced as (1) mutants off the shelf, (2) recombinants from an outcross to a wild-type strain (CS), (3) mutants as in Experiment 1 but with male types stored either together or separately, and (4) recombinants from a double outcross of flies from Experiment 2 to hybrids from two additional wild strains,LS andOR. Experiment 4 producedR andO males that courted nearly equally (as in previous experiments), in contrast with about 70% courtship byR males in the other experiments. Females discriminated in favor of those second to court in G₀, G₁, and a repeat of G₀; however, with two generations of inbreeding, discrimination by this criterion lessened to become nonsignificant. In Experiments 1 and 2,O females favored second-courting males, butR females in hose experiments and all females in Experiment 3 mated more randomly. Effects of storing males either together or separately were not significant. About 20–30% of the females (low threshold) were highly receptive immediately after first courtship. Those trials plus any in which only a single type of male courted were omitted from estimations of female discrimination; a possible bias incurred by such omission against females that might have initial preferences was found to be nonsignificant. Discriminating ability was discussed as a fitness property inDrosophila populations.This research was supported in part by National Science Foundation Grant DEB 79-03259.