Genetic Influences On Mating Behavior in Drosophila Melanogaster1)

[Certain aspects of mating behavior in two different types of Drosophila melanogaster females (Basc and Bv) and wildtype males (Samarkand) have been investigated. In one series of experiments (Series A), individual males were permitted to choose between two females of the two different genotypes only. In the second series (Series B) started about three years after the termination of the first, individual males were permitted to choose between (a) two females from the Bv strain, (b) two females from the Basc strain, or (c) a Basc and a Bv female. The three flies were observed over a period of 2 ¼ hours from the time they were placed together in a vial. No female copulated twice during this period. When the males copulated for the first time, the choice of partners was random; approximately 50% of the first copulations were with Bv and 50% with Basc females. When the first copulations were with Bv females, the type of the second female in the vial had little influence on the frequencies of the second copulations. However, when the Basc females were the first partners, the type of the second female in the vial did influence the frequencies of the second copulations; the males copulated more frequently a second time when the second was a Bv rather than a Basc female. Factors that might have accounted for the differences are discussed, including olfaction. When all four mating combinations in Series B (Basc-Basc, Basc-Bv, Bv-Bv, Bv-Basc) were compared, the premating periods hardly differend from each other, nor did the intermating periods. Both of these periods were shorter than the respective periods in Series A. Genetic changes (mutation and recombination) occurring during the three-year interval may have caused the females to be more receptive to the males in the later than in the earlier experiments. In Series A, the premating and intermating periods were both shorter when the first copulations were with Basc rather than with Bv females. Changes in heterogeneity may have decreased the advantage of the Basc females in these two categories. The durations of the second copulations were longer than those of the first with both types of females, and there was a positive correlation between the durations of the first and second copulations. The durations of the copulations depended to a great extent on the males but also were influenced by the females, as were the premating and intermating periods. Nearly twice as many offspring resulted from the first as from the second copulations., Certain aspects of mating behavior in two different types of Drosophila melanogaster females (Basc and Bv) and wildtype males (Samarkand) have been investigated. In one series of experiments (Series A), individual males were permitted to choose between two females of the two different genotypes only. In the second series (Series B) started about three years after the termination of the first, individual males were permitted to choose between (a) two females from the Bv strain, (b) two females from the Basc strain, or (c) a Basc and a Bv female. The three flies were observed over a period of 2 ¼ hours from the time they were placed together in a vial. No female copulated twice during this period. When the males copulated for the first time, the choice of partners was random; approximately 50% of the first copulations were with Bv and 50% with Basc females. When the first copulations were with Bv females, the type of the second female in the vial had little influence on the frequencies of the second copulations. However, when the Basc females were the first partners, the type of the second female in the vial did influence the frequencies of the second copulations; the males copulated more frequently a second time when the second was a Bv rather than a Basc female. Factors that might have accounted for the differences are discussed, including olfaction. When all four mating combinations in Series B (Basc-Basc, Basc-Bv, Bv-Bv, Bv-Basc) were compared, the premating periods hardly differend from each other, nor did the intermating periods. Both of these periods were shorter than the respective periods in Series A. Genetic changes (mutation and recombination) occurring during the three-year interval may have caused the females to be more receptive to the males in the later than in the earlier experiments. In Series A, the premating and intermating periods were both shorter when the first copulations were with Basc rather than with Bv females. Changes in heterogeneity may have decreased the advantage of the Basc females in these two categories. The durations of the second copulations were longer than those of the first with both types of females, and there was a positive correlation between the durations of the first and second copulations. The durations of the copulations depended to a great extent on the males but also were influenced by the females, as were the premating and intermating periods. Nearly twice as many offspring resulted from the first as from the second copulations.]