The adult component of selection in Drosophila melanogaster: some aspects of early-remating activity of females.

As an important factor of the adult component of selection, mating behaviour was studied in Drosophila melanogaster, with emphasis on non-virgin females. We found that 30-50 per cent of the females in a laboratory population will remate within 6 h of first mating under no-choice conditions. This high percentage of early rematings was not due to the continuous confinement of the females with males but indicated a rapid return of receptivity of a significant proportion of the females. Remating behaviour was significantly influenced by both the genotype of the female and the genotype of her two successive partners. Age of females was only important insofar as it concerned young, 1 or 2-day old, females. These females showed less remating than older females. Willingness to remate was also affected by the number of sperm stored. Females that had been inseminated by less fertile males, i.e. males that had already mated two or three times, showed higher remating percentages than females inseminated by more fertile males. Notwithstanding this sperm effect, females were estimated to remate approximately every second day. It is suggested that a high frequency of remating and the resulting sperm competition are significant components of Drosophila life-history.